When to lock CDL

[ProjectDirector]

I would like to open up a can of worms here[emoji16]
Over the last 2 years I have been teaching my son nearly 18 to drive on road of course many camping/hunting trips off road.
I have been telling him all along to lock cdl when getting off the tar but the gravel road needs to be loose and not compacted.
We tend to have many gravel roads that are very compacted before we get on to tracks with loose surface, soft, wet etc. so I believe indiscriminate use of cdl can cause wind up and failure in drivetrain

What are your thoughts and experiences?

[AK83]

According to Dave Ashcroft, whenever there's a chance of any wheel slip.
So to me that means even wet tarmac!

I had a '79RRC, and I wore out 2 centre diffs on it back in the early 90's.
Thinking of Ashcrofts words and the amount of gravel roads driving I did with that '79, it was inevitable that both those diff failures happened.

[Bearman]

Even corrugated dirt roads will cause wheel spin so good idea to lock it unless it is a flat and well compacted road.

[rangieman]

As above and the best thing is if your on one of theses compacted dirt roads and come across a loose / muddy what ever part you can select CDL on the fly [wink11].

[ProjectDirector]

Even corrugated dirt roads will cause wheel spin so good idea to lock it unless it is a flat and well compacted road.
Agree, I always lock it on corrugated roads.
When I bought the defender, i was offered a half day training by MCL at a location in around Werribee and the instructor there insisted that when off the tarmac lock the CDL, mmm?? I was scratching my head and ignored it.

[trout1105]

I had my Transfer box/CDL rebuilt a couple of years ago, Since then I have locked the CDL every time I have left the bitumen.
I haven't had any issues with "Wind Up" on the dirt even though some of the roads are hard packed at times and given that the alternative to not engaging the cdl is to face another expensive repair bill I will continue to do this.
Besides with the CDL engaged the D2a handles better on the dirt than with it not engaged. [thumbsupbig]

[rick130]

As usual, I'm the lone dissenting voice! [emoji23]

I hated the understeer a locked CDL gave on dirt in my 130, and I lived in the bush and drove dirt daily for over a decade with an unlocked CDL, and I drove it like I'd stole it, making the thing drift and slide most of the time.
My t/case didn't self destruct as a consequence.

The ultimate fix is an ATB replacing the open centre diff.
It improves dirt road performance significantly, eliminating the hunting you can sometimes get with an open diff as well as reducing the understeer you get with a locked diff.

[djam1]

I agree with Rick my earliest full time 4x4 Land Rover was an LT95 equiped 1974 Range Rover this was back in the early 80s
Since than I haven’t been one engage CDL because I drove on a dirt road (for years it would never of got out of CDL)
Never have I had a failure of a CDL have reshimmed a couple but never destroyed one.
There are certain corrugated circumstances that you should put it in CDL just like I put Land Cruisers in 4x4 these are extreme with the wheels cannon balling and the vehicle going no where. I have would doubt you would see this in the eastern states in the desert it was common.
The CDL is there to absorb slight differences use with a little common sense and they are quite durable.
With my Stage 1 I would spin the inside front wheel on bitumen quite regularly never had a failure.

[ProjectDirector]

As usual, I'm the lone dissenting voice! [emoji23]

I hated the understeer a locked CDL gave on dirt in my 130, and I lived in the bush and drove dirt daily for over a decade with an unlocked CDL, and I drove it like I'd stole it, making the thing drift and slide most of the time.
My t/case didn't self destruct as a consequence.

The ultimate fix is an ATB replacing the open centre diff.
It improves dirt road performance significantly, eliminating the hunting you can sometimes get with an open diff as well as reducing the understeer you get with a locked diff.

I dont disagree with you, but when the dirt road is compacted and smooth with no loose stones I dont lock it.

[cripesamighty]

I always found this video to be helpful. In the end it is your own choice, but it’s good in some situations and not others. Personally I’d love an ATB!

YouTube (https://m.youtube.com/watch?v=vFHCYuPTbfg)

[dazzler]

+ 1 ATB

Have switched to ATB all around and loving it, this thing is planted on any surface with/without CDL. From mem CDL did improve handling on loose stuff without ATB.

pd

[ozscott]

Probably the difference between a 100inch and 130 inch wheelbase but on long stretches of corrugated dirt I prefer CDL locked for more positive handling and throttle oversteer - plenty of drifting at Cape York fully loaded. Cheers

[ProjectDirector]

+ 1 ATB

Have switched to ATB all around and loving it, this thing is planted on any surface with/without CDL. From mem CDL did improve handling on loose stuff without ATB.

pd
Just out of curiosity, how does the ATB react when wheels are up in air?

[HardCharger]

When that happens, I remember reading somewhere that light left foot breaking will make the diffs "lock up" to negate any unnecessary spin and keep you moving.

ATBs and TC are said to be the dream combo! Will probably go this route when I finally get the coin for it.

[vnx205]

Just out of curiosity, how does the ATB react when wheels are up in air?

How many wheels in the air? I think it makes a difference.

[Zeros]

How many wheels in the air? I think it makes a difference.

3 [tonguewink][bigwhistle]

But seriously, I lock my cdl on corrugated, soft or wet dirt. I don’t lock it on hard smooth dirt or wet bitumen.

+ 1 saving for ATB

[tact]

How many wheels in the air? I think it makes a difference.
Doesn’t make a difference. If the CDL is unlocked - just one wheel loose (in air) and the whole driveline loses it. With or without ATBs in place.

With an Ashcroft ATB in the centre, the CDL(ock) still works and can be manually locked.

On very slippery surfaces I notice serious understeer with my 110 when the CDL is locked - in some circumstances (usually only when the loud pedal is getting a workout, or the front end is unloaded e.g. uphill).

I tend to modify the wisdom that says “engage CDL as soon as leaving tarmac” to “engage CDL whenever it is possible/likely for wild wheelspin to occur, regardless road surface (“includes wet tarmac)”.

[rick130]

Probably the difference between a 100inch and 130 inch wheelbase but on long stretches of corrugated dirt I prefer CDL locked for more positive handling and throttle oversteer - plenty of drifting at Cape York fully loaded. Cheers

The longer the wheelbase the slower/more stable the reactions with any fore/aft load transfer.

Way out west I found that the short wheel base and round shouldered HT tyres had the rear end in the D2 wanting to climb out of wheel ruts coming up to cattle grids under severe braking. Sideways coming into a cattle grid is, err, interesting. [tonguewink]
Too much speed had nothing to do with it. [bigwhistle]

When it gets a CDL and ATB it'll be interesting to feel the difference, but that's a fair way off.

[DiscoMick]

Would having TC affect the need to lock the CDL, do you think?

[rick130]

Would having TC affect the need to lock the CDL, do you think?

Absolutely, it's all about wheel spin.

[tact]

Would having TC affect the need to lock the CDL, do you think?
My understanding is that our stock centre diffs do not survive long if unlocked and one or more wheels are able to break loose and spin up.

I don’t have TC on my Defender. So it’s just a guess: if the TC worked real well at stopping wheels from breaking loose and spinning up, every time - then maybe that’s good enough.

[1nando]

Cant be bothered reading all replys so ill keep it simple;

Soon as your of the tarmac lock the centre diff!

See, easy

[dennisS1]

May not be in the majority with this but have been around a bit, and a lot of travel on gravel/sand. My answer is only when needed to proceed. Never over 40Km/h never on good surfaces, would never consider it on corrugations. Have had 1 Disco and 2 Defenders with over 800,000K combined and never had a problem with CDL’s.
Dennis

[weeds]

Age old question.......

I religiously engage mine....was doing it way before I was made awear of the physics around it.

Other don’t

Each to there own......

[Pedro_The_Swift]

regardless of your driving style(or lack thereof hey Rick!)
you should engage CDL regularly if only to ensure you CAN...

remember, if you dont use it...

[Zeros]

regardless of your driving style(or lack thereof hey Rick!)
you should engage CDL regularly if only to ensure you CAN...

remember, if you dont use it...

The CDL on my 20 year old Tdi is sweet because I’ve used it a lot. It’s slips in smooth nd positive on the fly and only ever needs a short reverse unwind to disengage if there have been a lot of slow tight twisty turns. I’ve always locked it on fast dirt up 80km/hr unless it’s compacted smooth like a highway.

The CDL on my 4 year old Puma is still tight, not as positive to shift and always requires a short reverse or two to unwind. I lock it st every opportunity but ..I definitely need to use it more! But circumstances have changed lately and I’m not living out bush at the moment so ...I need to get out more and lock the CDL in the too shiny newer beast!

[rick130]

regardless of your driving style(or lack thereof hey Rick!)
you should engage CDL regularly if only to ensure you CAN...

remember, if you dont use it...

And the same goes for low range for mostly highway drivers. [wink11]

[1nando]

Engaging the cdl as soon as your off tarmac will not damage the drive train. The extra wear is so minimal that it is negligible. However if you dont engage it and loose traction to the point where you spin a wheel for a few seconds you risk damaging the centre diff and it potentially locking up permanently...in which case you just broke it!
Engage the dam thing and she'll be right. The other thibg to consider is that off tarmac the vehicle is much safer with the cdl engaged. Increases traction through drive going to the front and the back. Especially safe on fast gravel or dirt

[ProjectDirector]

Wow I did open up a can of worms [emoji218]!!
I can now confirm that my CDL engagement is consistent with everyone here.
I do lock it soon as am off bitumen but there are occasions where the track is solid and smooth and no chance of slipping unless it is wet of course, all other times is locked in Hi or Lo.
On some occasions I need to reverse slightly to release light.
Cheers everyone

[dazzler]

Just out of curiosity, how does the ATB react when wheels are up in air?

I have TC so no issues, I have not experienced any traction loss after i installed the ATB's to be honest ..totally different driving experience on the loose stuff. But without TC you might want to use left foot braking with ATB. Neil he has ATB without TC.

pd

[Shoogs]

May not be in the majority with this but have been around a bit, and a lot of travel on gravel/sand. My answer is only when needed to proceed. Never over 40Km/h never on good surfaces, would never consider it on corrugations. Have had 1 Disco and 2 Defenders with over 800,000K combined and never had a problem with CDL’s.
Dennis

About same for me, a couple of 100k on dirt in Defenders, rarely engage it and never any issues, each to there own I suppose.

[ProjectDirector]

I have TC so no issues, I have not experienced any traction loss after i installed the ATB's to be honest ..totally different driving experience on the loose stuff. But without TC you might want to use left foot braking with ATB. Neil he has ATB without TC.

pd

Thanks for clarification, my 110 has TC (2013) so this could be something to consider.

[Zeros]

Thanks for clarification, my 110 has TC (2013) so this could be something to consider.

My TC light never comes on while driving fast dirt, yet an ATB would improve traction, as does locking the CDL. Still etter to lock CDL or get an ATB on dirt, even with TC, IMO. Also agree it’s a good idea to put it in low range regularly too.

[trout1105]

May TC light never comes on while driving fast dirt, yet an ATB would improve traction, as does locking the CDL. Still etter to lock CDL or get an ATB on dirt, even with TC, IMO. Also agree it’s a good idea to put it in low range regularly too.

I agree, The old saying "If you don't Use it you will Loose it" comes to mind [thumbsupbig]

[Landy Red]

Engage it as soon as you are driving on a surface you wouldn’t/shouldn’t drive a front wheel drive family sedan on. That's my rule. I don’t bother on well formed gravel roads, but as soon as I am on a track and suspect a bit wheel spin I push it across. I quite like the driver interaction with the vehicle of popping it across and back as the track conditions change. I leave it open on hard sand, but lock it in soft sand.

[rangieman]

Engage it as soon as you are driving on a surface you wouldn’t/shouldn’t drive a front wheel drive family sedan on. That's my rule. I don’t bother on well formed gravel roads, but as soon as I am on a track and suspect a bit wheel spin I push it across. I quite like the driver interaction with the vehicle of popping it across and back as the track conditions change. I leave it open on hard sand, but lock it in soft sand.
I would think any sand would require engagement [wink11]

[Landy Red]

I would think any sand would require engagement [wink11]

When it's really compact hard sand it feels a lot like concrete, so I tend not too.

[trout1105]

If you know the stretch of dirt you are travelling on is hard packed and there are No hidden surprises then leaving the CDL open isn't a problem.
However if you are unfamiliar with a stretch of dirt then it pays to have the CDL engaged because you never know when a washout, soft spot, loose stretch or creek crossing will pop up and usually by the time you hit the problem it is too late to engage the CDL.

[rangieman]

If you know the stretch of dirt you are travelling on is hard packed and there are No hidden surprises then leaving the CDL open isn't a problem.
However if you are unfamiliar with a stretch of dirt then it pays to have the CDL engaged because you never know when a washout, soft spot, loose stretch or creek crossing will pop up and usually by the time you hit the problem it is too late to engage the CDL.
And as Dave Ashcroft say`s it is only second`s between a operational CDL and a dead CDL[wink11]

[tact]

And as Dave Ashcroft say`s it is only second`s between a operational CDL and a dead CDL[wink11]
Here is the actual quote lifted from the Ashcroft site:
" If you are Off Road on snow or ice and you get wheelspin from one front wheel, what will happen is the rear prop will not be moving, the front will thus be going double speed, this means the small centre diff gears will be spinning like fury and after a matter of only a few seconds the planet gears will friction weld to the cross pins and the gears will fail etc. Of course in this situation the centre diff should be locked to avoid failure."

Its wheelspin that is the centre diff killer (not technically a CDL killer, the "L" is for Lock", the diff lock mechanism isn't destroyed by wheelspin).

Hence my suggestion to lock whenever there is chance of wheelspin - even if that is on wet tarmac, rock etc...

Reflecting on comments made in another thread about things written on the Ashcroft and Truetrac sites being authoritative, when I labelled some of it as being dumbed down or even "market spin":
The quote above, possibly from the second epistle of Ashcroft to the heathens at large, mentions:
"...when one front wheel" ...starts to wheelspin then centre diffs can melt in seconds.

At the risk of being labelled blasphemy, verily I say unto thee - This will apply to any REAR wheel breaking out into wheelspin too. Verily even if both rears or both fronts break into wheelspin.... destruction and perdition awaits.

(Just for a side of cheek with your main...: And ATBs still don't "need wheelspin to work" despite that not being explicit on the holy walls of Ashcroft or Detroit).

[DiscoMick]

Thanks.
So does that mean vehicles with effective TC such as my Puma should be less vulnerable because the TC stops the wheels from spinning?

[ProjectDirector]

Thanks.
So does that mean vehicles with effective TC such as my Puma should be less vulnerable because the TC stops the wheels from spinning?
Interesting question

[tact]

Interesting question

...so nice its now been asked twice. [bigwhistle]

[weeds]

Thanks.
So does that mean vehicles with effective TC such as my Puma should be less vulnerable because the TC stops the wheels from spinning?

I always thought traction control activates after the there is an imbalance between wheels (one spinning)

[Zeros]

Thanks.
So does that mean vehicles with effective TC such as my Puma should be less vulnerable because the TC stops the wheels from spinning?

Prevention is better than cure IMO, which is why I lock my CDL often and also partly why I’m saving $ for an ATB. ...as Weeds says, TC only stops a wheel slipping after it starts. It doesn’t do anything to strengthen the driveline.

[ninetubes]

Hang on, why are we concerned about spinning wheels on hard-pack gravel roads etc?

Can the CD not also be preserved by maintaining a driving style that's less flamboyant than Colin McRae?

[Zeros]

Hang on, why are we concerned about spinning wheels on hard-pack gravel roads etc?

Can the CD not also be preserved by maintaining a driving style that's less flamboyant than Colin McRae?

Because some hard packed gravel roads are not as they first seem, nor are they consistent + a locked CDL provides better traction regardless.

[trout1105]

Even in my old 4WD's without the benefit of a CDL I would engage 4WD once I got off the bitumen.
It can't do any harm to engage 4WD or the CDL and it makes good sense on the dirt, tracks or beach to be in 4WD anyway, Why wait until you get stuck or start spinning wheels.
You could rely solely on the traction control in the loose stuff But if you have a CDL why not use it, It's Not that hard to push the lever over.

[cripesamighty]

I got into the habit of flicking the lever across (when hitting anything that isn't bitumen) when driving my previous Defenders, and now do it in my D1 without much conscious effort. It's similar to flicking the gear lever to Sport mode in my D3 when slowing down and going through a roundabout or entering merging traffic (to avoid the 'pregnant pause').

[rick130]

Thanks.
So does that mean vehicles with effective TC such as my Puma should be less vulnerable because the TC stops the wheels from spinning?Yep, and remember the D2 was sans a CDL for a number of years. [emoji6]

[djam1]

Dont forget that all LT230 Centre Diffs are not equal
The post 2015 Pumas have the cheap 2 pinion arrangement that would be much more suceptible to damage.
Maybe these should be treated differently??
Bring on the ATBs

[Zeros]

Dont forget that all LT230 Centre Diffs are not equal
The post 2015 Pumas have the cheap 2 pinion arrangement that would be much more suceptible to damage.
Maybe these should be treated differently??
Bring on the ATBs

Is it definitely only post 2015?

[djam1]

JustinC will know I am not sure

[1nando]

This whole argument about solid gravel roads blah blah blah....if a roo steps out on a compact gravel road and you need to take evasive action then a locked centre diff will provide more vehicle control then a vehicle travelling with it unlocked. Believe me a "compact gravel road" wont be so compact at 70kms per hour when you throw the steering wheel hard to one side to avoid a collision, a washout, a roo or any other potential hazard. Lock the damn thing and drive with peace of mind.

If your that worried about it put a ATB in the thing and drive care free.

[DiscoClax]

"Swerve around a 'roo"... ? Nah... I won't do that. I'll brake VERY hard. But that steering wheel is staying straight until I'm down to running pace or less.

[rangieman]

"Swerve around a 'roo"... ? Nah... I won't do that. I'll brake VERY hard. But that steering wheel is staying straight until I'm down to running pace or less.
X2
Im with you on this [thumbsupbig]

[rick130]

This whole argument about solid gravel roads blah blah blah....if a roo steps out on a compact gravel road and you need to take evasive action then a locked centre diff will provide more vehicle control then a vehicle travelling with it unlocked. Believe me a "compact gravel road" wont be so compact at 70kms per hour when you throw the steering wheel hard to one side to avoid a collision, a washout, a roo or any other potential hazard. Lock the damn thing and drive with peace of mind.

If your that worried about it put a ATB in the thing and drive care free.

i call BS.

I lived in roo central, drove dirt roads every day for 20 years and the amount of BS I read here sometimes we need a bloody D12 CAT to get through.....

If you want to lock the bloody thing fine, but saying you need to lock it, inferring it's unsafe without is utter crap

[rick130]

"Swerve around a 'roo"... ? Nah... I won't do that. I'll brake VERY hard. But that steering wheel is staying straight until I'm down to running pace or less.


X2
Im with you on this [thumbsupbig]

This.

Unfortunately the old Deefer had more hits than Elvis, most at speeds under 50km/h

[DiscoClax]

This.

Unfortunately the old Deefer had more hits than Elvis, most at speeds under 50km/h"Character" :)

[djam1]

I think there is a great diversity of experience here
Many city drivers that probably find dirt roads a novelty others have lived for years in the bush where driving on dirt is a daily event.
A couple of thousand ks of dirt roads while you are on holidays or a weekend in the mountains is vastly different than living in Yuendumu for 20 odd years and different practices arise.
The Defender instructions are "The differential lock should only be engaged when traction is likely to be lost"
and "a single axle roller rig may be used up to 5 kmh The Differential Lock must be disengaged" covers it
Like wise the swerving for wild life most who live in the country dont do it, its better to hit roos, emus than roll a Defender over.

[1nando]

i call BS.

I lived in roo central, drove dirt roads every day for 20 years and the amount of BS I read here sometimes we need a bloody D12 CAT to get through.....

If you want to lock the bloody thing fine, but saying you need to lock it, inferring it's unsafe without is utter crap4x4 overland had a great clip on his youtube channel highlighting when to engage 4wd.

A defender is only ever spinning one wheel when the centre diff is unlocked.

Now lets think about this;
My family is in the car, im probably around 2.8 ton loaded, im on a gravel surafce which isnt ever solid hence why its gravel and not bitumen and I've left the centre diff unlocked. Now each to their own on how you handle a potential impact but to say that a unlocked defender has the same vehcile control as a locked one (CDL engaged) is the biggest load of BS ive ever heard. True 4wd requires the centre diff be locked.

Bruce Davis once told me years ago......once your off tarmac usr the CDL. But hey forums are for experts only and each expert has his own opinion. I bought a 4wd as a tourer and used the 4wd system as a safety measure, cause thats about the only safety measure you can use in a defender as it has nothing else.

Watch Andrews vid and watch the difference between a vehicle in true 4wd and a unlocked one and how they handle sliding and high manoeuvre situations differently. You may be suprised.

FyI next time your on a so called "solid gravel road" slam the brakes and tell me how solid it was when the wheels locked up......

[trout1105]

i call BS.

I lived in roo central, drove dirt roads every day for 20 years and the amount of BS I read here sometimes we need a bloody D12 CAT to get through.....

If you want to lock the bloody thing fine, but saying you need to lock it, inferring it's unsafe without is utter crap

I have lived in "Roo Central" for the last 15yrs, That's why the Missus and myself drive 4WD's and not the little townie buzz boxes nearly everyone else drives.
Using the 4WD's for touring is just an added benefit for us because a 4WD is essential to be able to use the roads around here especially in winter.
I don't use the CDL or engage 4WD on the Tojo around here in summer because the roads are all hard packed gravel/clay and I travel them pretty much every day But in winter or when I am traveling on an unknown dirt road I have always used 4WD and since owning the Discovery I have engaged the CDL.
Why do I do this?
I do this because that is why I bought the 4WD for in the first place and that's to have good control on loose or slippery surfaces, If I didn't engage 4WD/CDL I may as well be driving one of those townie buzz boxes.
Anyway if Ashcrofts recommends engaging CDL on loose surfaces I tend to respect his opinion over ANY member of an internet forum [bigwhistle]

[Arch]

I think there is a great diversity of experience here
Many city drivers that probably find dirt roads a novelty others have lived for years in the bush where driving on dirt is a daily event.
A couple of thousand ks of dirt roads while you are on holidays or a weekend in the mountains is vastly different than living in Yuendumu for 20 odd years and different practices arise.
The Defender instructions are "The differential lock should only be engaged when traction is likely to be lost"
and "a single axle roller rig may be used up to 5 kmh The Differential Lock must be disengaged" covers it
Like wise the swerving for wild life most who live in the country dont do it, its better to hit roos, emus than roll a Defender over.

I agree with this. I do like having CDLs locked for the stability they offer in braking and the occasion sideways drift over corrugations or pot holes. This is something no stability control or ATB setup will react to fast enough whereas a CDL is always there. But yes, if I lived on a road and knew it well, I probably wouldn't bother.

I find it interesting the comments from Ashcroft on the wear encountered inside the diff with one wheel spinning - you would think it wouldn't be a problem in a well lubricated unit... in my experience as a mech, I have not seen a failure that wasn't user driven.

[djam1]

Every Centre Diff failure I have seen has been in an LT95 I understand that the reason for failure is centrifugal force spinning the oil away from the critical components.
Might it be also that the engine oil recommendation for LT95s were a contributing factor?
I agree never seen a failed one that wasnt either driver apathy or ignorance

Another point is that there was a season of D2s that didnt have a CDL the manufacturer must of had reasonable confidence that the Centre Diff could survive. The TC was pretty rudimentry and took quite a bit of slip to get it to work.
Maybe these shouldnt be driven on dirt




I find it interesting the comments from Ashcroft on the wear encountered inside the diff with one wheel spinning - you would think it wouldn't be a problem in a well lubricated unit... in my experience as a mech, I have not seen a failure that wasn't user driven.

[Arch]

Every Centre Diff failure I have seen has been in an LT95 I understand that the reason for failure is centrifugal force spinning the oil away from the critical components.
Might it be also that the engine oil recommendation for LT95s were a contributing factor?
I agree never seen a failed one that wasnt either driver apathy or ignorance

Another point is that there was a season of D2s that didnt have a CDL the manufacturer must of had reasonable confidence that the Centre Diff could survive. The TC was pretty rudimentry and took quite a bit of slip to get it to work.
Maybe these shouldnt be driven on dirt

Well that is interesting about the LT95... yes it could have been the wrong spec, simply not enough oil or a manufacturing/design issue. We can only speculate as other diffs do perfectly well in an environment where the oil is spun away from the centre.

Yes, it was an interesting move on the D2s. I find this tend towards electronic traction controls is simple marketing. Some of it is very good to get you though the occasional problem... but not nearly as good as a diff lock. Interesting example of the G300 where the professional model despite all the fabulous trickery available to Mercedes, the professional has old school diff locks.

[Zeros]

...after reading some excellent comments here and hearing Dave Ashcrofts advice, I’ll now be locking my CDL on all dirt road surfaces, even seemingly hard packed ones, from now on.
...definitely until I’ve saved enough for ATB’s and perhaps even with ATB installed in some circumstances, as they strengthen diff centres.

[tact]

[...]A defender is only ever spinning one wheel when the centre diff is unlocked.

I think I get what you meant to say above (...that it only takes one wheel free spinning to unload the whole driveline, when centre diff is unlocked. Assuming also no TC etc).

Not quite true to say that a defender is only ever spinning one wheel, even it if is the most common scenario. It takes talent, skill, and devilishly good looks - but I have certainly had both fronts, both rears, or diagonals wheelspinning before cringing [bigsad] and remembering late to engage the CDL.




Now lets think about this;
[...]True 4wd requires the centre diff be locked.


Okaaaaaaaaay..... am calling this out too.
In a vehicle with open diffs (front, centre, rear) and no TC:
- Locking the centre diff just moves from the above situation (any ONE wheel freespinning unloads the whole drive train), to...
- a situation where the whole driveline is unloaded when ONE front and ONE rear are freespinning. (e.g. crossaxled)

"True 4wd" surely must require both front and rear diffs to be locked too. Locking just the centre diff is just a halfway step in that direction. Yes?

If locking the centre diff is such a good thing to do then locking all 3 diffs must be so much the better! Yes?

No.

I doubt anyone here will advocate locking all 3 diffs the moment you leave the tarmac - we all are so clever we know that we'd have a terrible time steering with all 3 diffs locked. Well.... not all the time, but sometimes.

Guess what... just locking the centre diff also has an undesireable side effect. It is just less tragic, less noticable, than driving around with all 3 diffs locked. It goes like this:
- we don't lock our centre diffs on the tarmac because we will get transmission wind up. We all know what causes that.
- if you jack up a wheel when there is significant transmission wind up present... just before that wheel leaves the tarmac it will slip/skid a bit and release the tension.
- on looser surfaces, even hard packed clay, that same little bit of wheel slippage on the track surface is going on and on and on - constantly as you drive down the trail.
- when there is no centre differential in play (not there, or locked) you are in effect going to have one wheel (any one of the 4, randomly) experiencing a little breaking of traction constantly.
- Is this "true 3 wheel drive"? Albeit somewhat "quantum" in nature since you can never really know which of the 4 wheels will be slipping at any specific instant. [bigwhistle]

- and under some situations this forced breaking of traction causes significant understeer. Not all the time, but certainly sometimes and its never a highly desireable handling trait.

This is also written up in the third epistle of Ashcroft to the unwashed about the benefits of the holy centre ATB:
"...when racing fast on a low traction surface, the vehicle will not handle well when locked but is likely to wheel spin when unlocked." (i.e. so buy an ATB from Ashcroft being the prescribed solution, so you can have the best of both worlds. Or possibly - leave the thing unlocked, don't be racing so hard on the throttle, avoid wheelspin that way and don't buy an ATB?)

One does not have to be "racing" and the surface does not have to be "low traction"... I have experienced sphincter clenching moments tootling along just a little too fast on a dirt road when a sneaky off-camber bit mid bend caught me by surprise - understeer causing me significant angst. Making me think that had I NOT locked the CDL - I'd have likely driven the bend much more comfortably with just a little "Tokyo drift" avoiding any one wheel wheelspinning wildly by lifting the throttle pedal just a little for balance.

I actually think the best handling situation is being able to drive all wheels differentially as needed on most surfaces - just avoiding wheelspin like the plague. For that open diffs will suffice if you have a good feel for the loud pedal to avoid wild wheelspin. If lacking that skill then:
- the poorest solution is to take all diffs out of the equation (3 locked)
- less poor but still not the best, take just the centre diff out of the equation (lock it, live with having a random wheel breaking traction at every moment)
- best driver aid being to fit ATBs all round to allow differentiation and control (within its limits) wheelspin.

If the only tool in the toolkit is a hammer (or a centre diff lock), then the best you might be able to do is to be wise about when to use it. When to lock the CDL. And when not to.

[Zeros]

Very nice work Quantum Neil.

Roger. As said, Lock CDL off tarmac. Get ATBs asap. :)

[1nando]

I think I get what you meant to say above (...that it only takes one wheel free spinning to unload the whole driveline, when centre diff is unlocked. Assuming also no TC etc).

Not quite true to say that a defender is only ever spinning one wheel, even it if is the most common scenario. It takes talent, skill, and devilishly good looks - but I have certainly had both fronts, both rears, or diagonals wheelspinning before cringing [bigsad] and remembering late to engage the CDL.




Okaaaaaaaaay..... am calling this out too.
In a vehicle with open diffs (front, centre, rear) and no TC:
- Locking the centre diff just moves from the above situation (any ONE wheel freespinning unloads the whole drive train), to...
- a situation where the whole driveline is unloaded when ONE front and ONE rear are freespinning. (e.g. crossaxled)

"True 4wd" surely must require both front and rear diffs to be locked too. Locking just the centre diff is just a halfway step in that direction. Yes?

If locking the centre diff is such a good thing to do then locking all 3 diffs must be so much the better! Yes?

No.

I doubt anyone here will advocate locking all 3 diffs the moment you leave the tarmac - we all are so clever we know that we'd have a terrible time steering with all 3 diffs locked. Well.... not all the time, but sometimes.

Guess what... just locking the centre diff also has an undesireable side effect. It is just less tragic, less noticable, than driving around with all 3 diffs locked. It goes like this:
- we don't lock our centre diffs on the tarmac because we will get transmission wind up. We all know what causes that.
- if you jack up a wheel when there is significant transmission wind up present... just before that wheel leaves the tarmac it will slip/skid a bit and release the tension.
- on looser surfaces, even hard packed clay, that same little bit of wheel slippage on the track surface is going on and on and on - constantly as you drive down the trail.
- when there is no centre differential in play (not there, or locked) you are in effect going to have one wheel (any one of the 4, randomly) experiencing a little breaking of traction constantly.
- Is this "true 3 wheel drive"? Albeit somewhat "quantum" in nature since you can never really know which of the 4 wheels will be slipping at any specific instant. [bigwhistle]

- and under some situations this forced breaking of traction causes significant understeer. Not all the time, but certainly sometimes and its never a highly desireable handling trait.

This is also written up in the third epistle of Ashcroft to the unwashed about the benefits of the holy centre ATB:
"...when racing fast on a low traction surface, the vehicle will not handle well when locked but is likely to wheel spin when unlocked." (i.e. so buy an ATB from Ashcroft being the prescribed solution, so you can have the best of both worlds. Or possibly - leave the thing unlocked, don't be racing so hard on the throttle, avoid wheelspin that way and don't buy an ATB?)

One does not have to be "racing" and the surface does not have to be "low traction"... I have experienced sphincter clenching moments tootling along just a little too fast on a dirt road when a sneaky off-camber bit mid bend caught me by surprise - understeer causing me significant angst. Making me think that had I NOT locked the CDL - I'd have likely driven the bend much more comfortably with just a little "Tokyo drift" avoiding any one wheel wheelspinning wildly by lifting the throttle pedal just a little for balance.

I actually think the best handling situation is being able to drive all wheels differentially as needed on most surfaces - just avoiding wheelspin like the plague. For that open diffs will suffice if you have a good feel for the loud pedal to avoid wild wheelspin. If lacking that skill then:
- the poorest solution is to take all diffs out of the equation (3 locked)
- less poor but still not the best, take just the centre diff out of the equation (lock it, live with having a random wheel breaking traction at every moment)
- best driver aid being to fit ATBs all round to allow differentiation and control (within its limits) wheelspin.

If the only tool in the toolkit is a hammer (or a centre diff lock), then the best you might be able to do is to be wise about when to use it. When to lock the CDL. And when not to. With centre diff unlocked power only ever goes to either the front or rear axle not both at the same time. So your comment about having all wheels spinning with a open centre diff means that the TC is working to lock the spinning wheel cause your prop shaft is spinning around stupidly and all of a sudden power goes to the next axle where there is the least resistance causing that wheel to spin, prop spins stupidly again all before the TC does its job again.....this will go on until you blow the centre diff. This is a fact and needs to be understood! Dave Ashcroft explains this in a youtube video!

A defender is not a AWD subaru! So dont say it is cause thats what your implying it to be, BS! It does not automatically send power to both front and rear axles at the same time unless the centre diff is locked. This is why people install atbs!

The amount of BS on this site drives me insane. Tact i respect the majority of your input most times but you've missed the mark on this one mate. I stopped reading after your comment on all 4 wheels spinning with the centre diff unlocked.

As for locking all 3 diffs for better control. Of course you wouldnt do that. Only time i did was in very slow, extremely complicated terrain requiring zero steering input where loss of traction was expected.

Rally cars have a very sophisticated AWD system becuase it helps keep the car stable and controllable on fast dirt, snow, gravel etc.....but according to most on this site they should all be driving a unlocked (centre diff) defender. Its not BS to state that a defender has much better vehicle control off tarmac with the CENTRE DIFF LOCKED and staying at speeds around 80kmph or less.

[1nando]

YouTube (https://youtu.be/EBmw6Wpfe6M)

Clearly states that as soon as you hit dirt you should engage true 4wd!

Please watch, marvel, swallow pride and move on people! Almost forgot.....lock the damn centre diff when off the tarmac!

[trout1105]

YouTube (https://youtu.be/EBmw6Wpfe6M)

Clearly states that as soon as you hit dirt you should engage true 4wd!

Please watch, marvel, swallow pride and move on people! Almost forgot.....lock the damn centre diff when off the tarmac!

What a Good video, Even the lesser cranially empowered should be able to understand why Locking the CDL is important after watching this [thumbsupbig]

[tact]

What a Good video, Even the lesser cranially empowered should be able to understand why Locking the CDL is important after watching this [thumbsupbig]

Oh my giddy aunt! All the skid pan stuff in that video was comparing 2wd to 4wd in a vehicle with no centre diff at all!

The first bit showing a vehicle with a centre diff (the Defender) not going anywhere when one wheel is lifted has absolutely zero to do with what went on later in the video with a vehicle in 2wd and no centre diff.

A vehicle with a centre diff, unlocked, would have blitzed that skid pan course! Likely better than had it been locked! But that WASN’T what was being demonstrated in that video

[1nando]

True 4wd drive spilts power 50/50 between the front and rear axle. It is impossible to have 50/50 power split between axles with a open centre diff.
A defender with a unlocked centre diff will always send power to the one wheel with the least resistance on which ever axle that may be (front or rear). When the power is split evenly between the axles (front and rear) then true 4wd is engaged and the wheel with least resistance will drive on each axle. This allows one to drive through fast corners with more controll and stability.

The video clearly shows that....


Oh my giddy aunt! All the skid pan stuff in that video was comparing 2wd to 4wd in a vehicle with no centre diff at all!

The first bit showing a vehicle with a centre diff (the Defender) not going anywhere when one wheel is lifted has absolutely zero to do with what went on later in the video with a vehicle in 2wd and no centre diff.

A vehicle with a centre diff, unlocked, would have blitzed that skid pan course! Likely better had it been locked! But that WASN’T what was being demonstrated in that video

[trout1105]

A vehicle with a centre diff, unlocked, would have blitzed that skid pan course!
What a load of old cobblers.
With the centre diff unlocked an all wheel drive is NOT a 4WD and will react on that skid pan exactly the same as a standard 4WD running in 2WD mode.
Obviously you haven't got a basic understanding of how the CDL works on a Landrover yet, I suggest that you Watch that video again [thumbsupbig]

[tact]

With centre diff unlocked power only ever goes to either the front or rear axle not both at the same time.


Gotta stop you right there. That is flat out wrong. The whole point of having a centre diff is to drive all 4 wheels, even on tarmac, avoiding transmission wind up.

Are you so confused you are missing the difference between “full time 4wd” and “part time 4wd” systems??

No point touching on the rest of your comments til you get that part right in your head.

Utterly basic stuff here:
Part time 4wd: only one axle (front or rear) is driven, effectively 2wd, until the transfer box control is used to select 4wd. Most basic models have no centre diff - thus two modes:
- 2wd, for use on hard surfaces
- 4wd, for use ONLY when off tarmac

Full time 4wd: has a centre diff. Drives all 4 wheels whether the centre diff is locked or not. Two basic modes:
- 4wd, CDL UNLOCKED - for use on hard surfaces. Allows full 4 wheel differentiation so no transmission windup. Comes to grief if and only if a wheel is in the air and can free spin. At ALL other times when 4 wheels are on the ground, ALL 4 wheels are driven.
- 4wd, CDL LOCKED - for use ONLY when off tarmac.

[bee utey]

Wow, this thread is hilarious. Some people need to take a deep breath and step back a bit, maybe go for a drive on a muddy track somewhere far away from their internet connection. [biggrin]

[1nando]

Gotta stop you right there. That is flat out wrong. The whole point of having a centre diff is to drive all 4 wheels, even on tarmac, avoiding transmission wind up.

Are you so confused you are missing the difference between “full time 4wd” and “part time 4wd” systems??

No point touching on the rest of your comments til you get that part right in your head.

Utterly basic stuff here:
Part time 4wd: only one axle (front or rear) is driven, effectively 2wd, until the transfer box control is used to select 4wd. Most basic models have no centre diff - thus two modes:
- 2wd, for use on hard surfaces
- 4wd, for use ONLY when off tarmac

Full time 4wd: has a centre diff. Drives all 4 wheels whether the centre diff is locked or not. Two basic modes:
- 4wd, CDL UNLOCKED - for use on hard surfaces. Allows full 4 wheel differentiation so no transmission windup. Comes to grief if and only if a wheel is in the air and can free spin. At ALL other times when 4 wheels are on the ground, ALL 4 wheels are driven.
- 4wd, CDL LOCKED - for use ONLY when off tarmac.Tact; i suggest you place your vehcile in a situation where one wheel is up of the ground. Leave centre diff unlocked and release the clutch slowly in 1st and tell me what happens. The opposite axle will not have power transfered to it unless the TC cuts in and even then its assuming that axle has the wheel with least resistance.

Again; a defender is not a Subaru AWD vehicle where the transmission and computer are able to send power to whatever wheel on which ever axlel has traction automatically.

[djam1]

Are they allowed to lock thier centre diffs in the mud??


Wow, this thread is hilarious. Some people need to take a deep breath and step back a bit, maybe go for a drive on a muddy track somewhere far away from their internet connection. [biggrin]

[scarry]

Tact; i suggest you place your vehcile in a situation where one wheel is up of the ground. Leave centre diff unlocked and release the clutch slowly in 1st and tell me what happens. The opposite axle will not have power transfered to it unless the TC cuts in and even then its assuming that axle has the wheel with least resistance.

Again; a defender is not a Subaru AWD vehicle where the transmission and computer are able to send power to whatever wheel on which ever axlel has traction automatically.

Ok,i am no expert,just part of the audience here,talking about no traction control,Defender as an example,
We know what happens when one wheel loses traction,
But what happens when the vehicle is driving in a straight line,on bitumen,all wheels have grip,Cdl unlocked?

Through which wheel does the torque go?

At a guess i would say more than one,maybe even all four,unlike a 2wd vehicle?

That is why part time 4WD(no centre diff) is completely different from full time 4WD.

[JoeFriend]

Tact; i suggest you place your vehcile in a situation where one wheel is up of the ground. Leave centre diff unlocked and release the clutch slowly in 1st and tell me what happens. The opposite axle will not have power transfered to it unless the TC cuts in and even then its assuming that axle has the wheel with least resistance.

Again; a defender is not a Subaru AWD vehicle where the transmission and computer are able to send power to whatever wheel on which ever axlel has traction automatically.I don't usually try to explain other people's points, but essentially I am reading the situation to be;

You are saying an open centre diff will send power to one propshaft if it has less resistance on it than the other one.

Tact is possibly trying to say that an open centre diff CAN send power to both axles, provided they both have equal amounts of traction on both wheels.

What everyone is arguing about is whether or not to lock the CDL if there is a possibility you will lose traction on one wheel.

We can all agree that if there is a possibility of one wheel spinning, it's probably best to lock the CDL.

What none of you seem to agree on is when that point is.

Do I have this pretty much summed up? Cause if I do, arguing something like this is pretty much a zero sum game.

I recall a thread on winch pulleys that was like this. Can we bring tire size into this somehow as well? Possibly LED vs HID vs Halogen, expensive brand names VS cheaper copies.

Out of all the ridiculous arguments you could have, I think the only one there will be consensus with on this forum is Land Rover VS Land Cruiser.

[1nando]

Gotta stop you right there. That is flat out wrong. The whole point of having a centre diff is to drive all 4 wheels, even on tarmac, avoiding transmission wind up.

Are you so confused you are missing the difference between “full time 4wd” and “part time 4wd” systems??

No point touching on the rest of your comments til you get that part right in your head.

Utterly basic stuff here:
Part time 4wd: only one axle (front or rear) is driven, effectively 2wd, until the transfer box control is used to select 4wd. Most basic models have no centre diff - thus two modes:
- 2wd, for use on hard surfaces
- 4wd, for use ONLY when off tarmac

Full time 4wd: has a centre diff. Drives all 4 wheels whether the centre diff is locked or not. Two basic modes:
- 4wd, CDL UNLOCKED - for use on hard surfaces. Allows full 4 wheel differentiation so no transmission windup. Comes to grief if and only if a wheel is in the air and can free spin. At ALL other times when 4 wheels are on the ground, ALL 4 wheels are driven.
- 4wd, CDL LOCKED - for use ONLY when off tarmac.YouTube (https://youtu.be/kgScHqrLlEc)

Check mate!

Watch what happens when he unlocks the centre diff. The front wheel just keeps spinning. There is no wheel spining on the rear axle! The rear axle has more resistance than the front so only one wheel will ever spin. Soon as he locks the centre diff the rear axle gets 50% of the power and the vehcile moves forward. With the CDL unlocked only one wheel will ever spin on a defender!!!!

It is not a true AWD vehcile with an open centre diff Tact!

As for safety anyone who reckons its safe to travel on a surface without the equivalent frcition to that of tarmac with the CDL disengaged needs to learn the benefits of true 4wd. Its 100% safer to drive a vehcile in true 4wd on a non tarmac surface

[DiscoMick]

In 4WD with an open centre diff all four wheels are driven unless one or more wheels spin. Then the amount of power going front to rear can vary wildly
With the CDL locked the front to rear split is fixed at 50:50. Even if say a rear wheel spins the amount of power going front to rear is still 50:50.
TC then stops that wheel from spinning.
I often, but not always, lock the CDL on unsealed roads. Having TC helps. In high range I might lock it on skatey or corrugated roads. In low range I usually lock the CDL.
A Defender in low range with CDL locked, TC and anti-stall doesn't have much of a problem with wheelspin, in my experience.

[rangieman]

Oh this is so funny some need some education in CDL operation obviously Mr T[bigrolf]

[Zeros]

Umm...1nando, i watched the vid ...in that situation you would defiinately have the CDL locked anyway.

...On bitumen I reckon it would be a pretty rare occurence to have two wheels in the air LOL - on bitumen front and rear wheels are being driven, enabled by centre diff (different to a Tojo with front hubs unlocked - 2WD).

[AK83]

With centre diff unlocked power only ever goes to either the front or rear axle not both at the same time. .....

Well, yes, but at the same time no!
When one wheel is unloaded like AStPW showed(wheel in the air) of course this happens, but it doesn't always happen on a gravel road, as the guys have already noted.
Many moons ago, my dad had an 8t fridge van truck that used to play up in the morning. To get him going he enlisted my help in the RRC(LT95 back then, but same difference when I fitted a LT77+LT230).
The driveway was about 50m all gravel(red scoria to be exact). The first 10m pulling the truck, diff unlocked 2nd low, always had the RRC spin one front and one back wheel. But it would pull and spin and pull and spin .. etc.
There was just enough traction to get some momentum, but also not quite enough to have tarmac like grip. But definitely used to get one front AND one rear spin up every time.
What you relating is when you definitely have a situation where one wheel is going to have far less grip than any of the other 3.
That argument is not about gravel road driving.
What AStPW showed in that video is '4WD', not 'gravel road driving' as discussed by many and sundry.

It was Rick130 that commented on the understeer when the CDL was locked.
In my Rodeo ute, I had the same annoyance on gravel. Long wheel base gave understeer all the time, unless a lot of right foot was used to deliberately minimise it, but with the transfer set to 4WD(and front hubs locked), it became pig understeer. I hated it.
Same with the Frontera I had after that too. Much less pig understeer than the rodeo, as it had a shorter wheel base. In 2WD mode(it had a rear LSD) it could be balanced OK(nothing like a Disco or RRC) but with the 4WD switch set, a bit too much understeer.
Frontera and Rodeo are not renown for handling excellence too tho!

On a flowing gravel road where the chances of lifting a wheel is pretty much zero, you will get pretty much 50/50 drive split between axles with centre diff unlocked.
On a 4WD track, where you find boulders that can lift a wheel, obviously an open centre diff isn't the ideal way of tackling the obstacle.


Oh this is so funny some need some education in CDL operation obviously Mr T[bigrolf]

I reckon the humorous turn in the thread is due to the possible misunderstanding as to what type of gravel road driving is being discussed.
I took it to relate to fast flowing gravel road driving, not the type that may throw up an obstacle like a boulder that could see a wheel lifted.
To me, the second example wouldn't usually be described as a gravel road, but more as a track .. 4WD track.
Hard packed gravel road, understeer, and references to that effect usually equate to fast flowing gravel roads.

[rangieman]

Well, yes, but at the same time no!
When one wheel is unloaded like AStPW showed(wheel in the air) of course this happens, but it doesn't always happen on a gravel road, as the guys have already noted.
Many moons ago, my dad had an 8t fridge van truck that used to play up in the morning. To get him going he enlisted my help in the RRC(LT95 back then, but same difference when I fitted a LT77+LT230).
The driveway was about 50m all gravel(red scoria to be exact). The first 10m pulling the truck, diff unlocked 2nd low, always had the RRC spin one front and one back wheel. But it would pull and spin and pull and spin .. etc.
There was just enough traction to get some momentum, but also not quite enough to have tarmac like grip. But definitely used to get one front AND one rear spin up every time.
What you relating is when you definitely have a situation where one wheel is going to have far less grip than any of the other 3.
That argument is not about gravel road driving.
What AStPW showed in that video is '4WD', not 'gravel road driving' as discussed by many and sundry.

It was Rick130 that commented on the understeer when the CDL was locked.
In my Rodeo ute, I had the same annoyance on gravel. Long wheel base gave understeer all the time, unless a lot of right foot was used to deliberately minimise it, but with the transfer set to 4WD(and front hubs locked), it became pig understeer. I hated it.
Same with the Frontera I had after that too. Much less pig understeer than the rodeo, as it had a shorter wheel base. In 2WD mode(it had a rear LSD) it could be balanced OK(nothing like a Disco or RRC) but with the 4WD switch set, a bit too much understeer.
Frontera and Rodeo are not renown for handling excellence too tho!

On a flowing gravel road where the chances of lifting a wheel is pretty much zero, you will get pretty much 50/50 drive split between axles with centre diff unlocked.
On a 4WD track, where you find boulders that can lift a wheel, obviously an open centre diff isn't the ideal way of tackling the obstacle.



I reckon the humorous turn in the thread is due to the possible misunderstanding as to what type of gravel road driving is being discussed.
I took it to relate to fast flowing gravel road driving, not the type that may throw up an obstacle like a boulder that could see a wheel lifted.
To me, the second example wouldn't usually be described as a gravel road, but more as a track .. 4WD track.
Hard packed gravel road, understeer, and references to that effect usually equate to fast flowing gravel roads.
All this dick waiving is just making it way to complicated when it is not rocket science at the end of the day .
Just lock the cdl when traction is likely to be lost and that icl wet skid pads FFS[bighmmm]

[AK83]

.... Just lock the cdl when traction is likely to be lost and that icl wet skid pads FFS[bighmmm]

[thumbsupbig]

Going by Dave Ascrosft's comments, I now just do just as a matter of forcing myself into a habit.
if the gravel section is short, I don't.
eg. some months back up the Silver City hwy, it's basically all bitumen, but one small section near a research station was gravel. Even tho I have it in my mind to set the CDL to lock on gravel, for the 5-10klms of gravel not worth the effort.
But doing hundreds or thousands of klms on, hard packed, fast flowing gravel .. even tho I know I don't really need it!, I still lock it anyhow.

Now(the question needs to be asked)!! .. where do we find these skid pads to have some fun on? [biggrin]

[MarkM]

1nando says...True 4wd drive spilts power 50/50 between the front and rear axle. It is impossible to have 50/50 power split between axles with a open centre diff.

I am a bit hesitant to add fuel to the fire here, but will anyway. I dont think the above, and some other posts are perfectly accurate

Physics...

Power = torque x speed

Ignoring internal friction in the drivetrain, I actually think that with no front or rear locker and CDL unlocked, the vehicle shares torque equally amongst the 4 wheels and speed in each is independent. In conditions where a wheel may slip, the torque in the system is limited to the torque that the wheel with least traction can apply, and all others receive this much torque. In a circumstance where one wheel is no longer in contact with the ground, and assuming no application of the brakes either by man or machine, then all wheels receive zero torque. So if in slipping conditions one wheel has some traction but is slipping, then this will be going at higher speed, with same torque, so will get more power. The 3 others get same torque, less speed, less power.

With the CDL locked, the speed in the front and rear propshafts is equal, and with no other locking diffs, then torque is shared equally left and right in each of the axles, but torque in front may be different to rear. Within each axle torque is same left and right, but speed may be different

And, my driving, which is based on opinion, and less experience than others here....

Depends on the circumstances. For example on sand, when travelling alone, and with no winch, no maxtracks etc, ( a long time ago) I always preferred to drive my RRC with diff unlocked, so that if i started to get into trouble I would get some warning of trouble, and have something to "deploy" i.e. CDL, rather than drive with CDL locked, get bogged and then have nothing but a shovel to attack the problem with.

And a closing thought

I think there are too many differing circumstances in the real world to be able to reduce this a simple blanket rule, which is why there are differing opinions in this thread. Its also why you can't learn all this stuff with 5 minutes of experience, and thats what keeps us all interested.

Mark
edited 'cause I can't quote competently

[trout1105]

Depends on the circumstances. For example on sand, when travelling alone, and with no winch, no maxtracks etc, ( a long time ago) I always preferred to drive my RRC with diff unlocked, so that if i started to get into trouble I would get some warning of trouble, and have something to "deploy" i.e. CDL, rather than drive with CDL locked, get bogged and then have nothing but a shovel to attack the problem with.


I found (From experience) that waiting until you need 4WD to engage it is a recipe for disaster in sand because by the time you have engaged 4WD/Locked the CDL it is usually far too late.
I see examples of this every holiday season where people get bogged and THEN engage 4WD to try and get out of trouble, The sands on WA beaches are Not that forgiving and I have seen people hopelessly bogged in sections of sand where if they were in 4WD mode they would have had absolutely no difficulty getting through.
I would think that everyone who lives in the Geraldton area that has been to the Greenough river mouth has seen this sort of thing happening at one time or another.
The same applies for many of the popular beach areas, Inskip point is well known for its bogging's and I wager that many of those bogging's are a direct result of failing to engage 4WD until it is too late.

If you are doing any beach driving ALWAYS engage 4WD/CDL and drop your tyre pressures to suit the conditions.
YES it is a PITA pumping up your tyres again when exiting the beach But it is No hardship putting the truck into true 4WD mode and doing this is much more preferable to swinging on a shovel in the middle of summer and retrieving the buried maxtracks or worse Begging someone to pull you out of the mess (That's IF you can find anyone).

[1nando]

1nando says...True 4wd drive spilts power 50/50 between the front and rear axle. It is impossible to have 50/50 power split between axles with a open centre diff.

I am a bit hesitant to add fuel to the fire here, but will anyway. I dont think the above, and some other posts are perfectly accurate

Physics...

Power = torque x speed

Ignoring internal friction in the drivetrain, I actually think that with no front or rear locker and CDL unlocked, the vehicle shares torque equally amongst the 4 wheels and speed in each is independent. In conditions where a wheel may slip, the torque in the system is limited to the torque that the wheel with least traction can apply, and all others receive this much torque. In a circumstance where one wheel is no longer in contact with the ground, and assuming no application of the brakes either by man or machine, then all wheels receive zero torque. So if in slipping conditions one wheel has some traction but is slipping, then this will be going at higher speed, with same torque, so will get more power. The 3 others get same torque, less speed, less power.

With the CDL locked, the speed in the front and rear propshafts is equal, and with no other locking diffs, then torque is shared equally left and right in each of the axles, but torque in front may be different to rear. Within each axle torque is same left and right, but speed may be different

And, my driving, which is based on opinion, and less experience than others here....

Depends on the circumstances. For example on sand, when travelling alone, and with no winch, no maxtracks etc, ( a long time ago) I always preferred to drive my RRC with diff unlocked, so that if i started to get into trouble I would get some warning of trouble, and have something to "deploy" i.e. CDL, rather than drive with CDL locked, get bogged and then have nothing but a shovel to attack the problem with.

And a closing thought

I think there are too many differing circumstances in the real world to be able to reduce this a simple blanket rule, which is why there are differing opinions in this thread. Its also why you can't learn all this stuff with 5 minutes of experience, and thats what keeps us all interested.

Mark
edited 'cause I can't quote competentlyYour wrong about your cdl engagement on the beach Mark. You are less likely to get bogged with the cdl locked on sand, also less likely to do damage the diff itself.

Your other comment in regards to the drivetrain is pretty acurate. I dumbed it down saying 50/50 as its close too but has variables. However one wheel will only ever spin at a time with cdl unlocked. It could be any one of the 4 wheels but never 2 at the same time on separate axles with it unlocked centre diff.

The defender has a permanent 4wd system not an all wheel drive system. There is a massive difference. When tact quoted that he'd had the front and rear wheels both spinning at the same time with the cdl unlocked this isnt possible. Key words: same time. It is not an all wheel drive. The only way this could happen is either with a centre diff atb or similar installed or with the cdl locked.

[ozscott]

I have done quite a lot of beach driving over the years including towing. Initially my D2 did not have CDL. As good as it was it was better again with CDL retrofitted. I always engage it on the beach, even hard sand, and drop tyre pressures. I would never wait until I'm in trouble and then lock. With the D2 bogging down and then deciding to lock the centre diff isn't going to be much help and if you are towing chances are you are well stuck and need to break out the shovel and drop the tyres down to silly levels just to get out and then have to pump them up (but not to road pressures) before moving on. Now throw in an incoming tide and holding up your mates and it's just not a good idea IMHO.

There is also more vehicle sympathy in having CDL locked in soft sand or hard sand where soft bits will be encountered versus the likely prospect of one wheel spinning like a top with CD open.

Cheers

[tact]

Tact; i suggest you place your vehcile in a situation where one wheel is up of the ground. Leave centre diff unlocked and release the clutch slowly in 1st and tell me what happens. The opposite axle will not have power transfered to it unless the TC cuts in and even then its assuming that axle has the wheel with least resistance.

[...]

We say the same thing about this... one wheel up means no drive when the centre diff is unlocked. (I don't have TC btw)....
(how about you jack up one wheel on the front axle, and one wheel on the rear axle, and tell me how well your "true 4x4" moves... you already know the answer)

None of the above relates at all to driving down a hardpacked dirt (or loose gravel) road at some respectable speed with the CDL unlocked. In that circumstance I rarely have a wheel off the deck. Not sure how you drive?

Glad you feel safer knowing that you'd need to raise one front AND one rear with the CDL locked. Whereas dolts like me will be in dire trouble if we dared to raise just one, any ONE, wheel off the deck.... (I manage to cope with the terrible risk of an unlocked CDL - by reflecting carefully on how many times I have been driving down a dirt road with a wheel in the air...)

In that circumstance: i.e. all wheels present and accounted for on the deck, CDL unlocked... all 4 wheels do get drive. Hence the moniker "full time 4wd". All wheels can travel different distances without any transmission wind up because of diffs present and open - front, centre and rear. And the side benefit - no increase in tendency to understeer as happens with CDL locked.

(Yes - if I raised up one wheel off the deck all that changes and drive to the remaining 3 wheels drops to zero - but you have to just take my word for it.... I personally don't raise wheels from the deck when tootling down a dirt road.)

I also do not agree that the skid pan exploits in the video has anything to do with how a full time 4wd will behave with the centre diff unlocked.

That video features a part time 4wd vehicle - first in 2wd mode (it can only drive the rear wheels), then in 4wd mode. Patently not an apples to apples comparison to an all wheel drive: first with CDL unlocked, then locked.

[B.S.F.]

Driving a Defender off the bitumen seems to be very complicated. I don't think I'd ever get the hang of it. I better stick to driving a series L/R.
.W.

[weeds]

Driving a Defender off the bitumen seems to be very complicated. I don't think I'd ever get the hang of it. I better stick to driving a series L/R.
.W.

Yeah it’s complicated........might sell mine.

[jackdef90]

This is why I stopped looking at this site. The pointless duscussions just drive me mad. Go and fist fight each other and be done with it

[pop058]

This is why I stopped looking at this site. The pointless duscussions just drive me mad. Go and fist fight each other and be done with it

Yet here "we" are [biggrin]

[ozscott]

Its just robust debate. Many of us enter the fray at times. We would all sit round a fire and have a laugh I'm sure.

Cheers

[rangieman]

Yeah it’s complicated........might sell mine.
Seem`s that way [bigwhistle]

[trout1105]

This is why I stopped looking at this site. The pointless duscussions just drive me mad. Go and fist fight each other and be done with it

You may find the discussion "Pointless" and you have every right to think what you like on this matter But many here Do think that how the CDL is used on their landrovers IS worth discussing so your negativity isn't adding anything useful to the discussion at all.

As for starting a "Fist Fight" over this well I think that is a silly notion, None of us here want to start a third world war over ANY subject matter being discussed on the forum.
It may be that we have differing opinions on a range of subjects from time to time and that is a GOOD thing because many of us won't just accept things just because someone says it is 'Kosher" and follow along like Sheep, Isn't that one of the reasons why we own a Landrover in the first place [bigwhistle]

[rangieman]

Its just robust debate. Many of us enter the fray at times. We would all sit round a fire and have a laugh I'm sure.

Cheers
And a Beer or 3:twobeers:

[Zeros]

Does anyone really think it’s a PITA to lock the CDL? I mean it’s not like you need to get off the couch to change the channel! Or out of the vehicle to lock the hubs! Hilarious.
...I love locking my CDL at every opportunity. It’s what makes it a Land Rover!

...now another can of worms :) ...at what max speed can you lock the CDL on the fly? And what’s the max speed you can drive with it locked? My rule of thumb has been 60kmhr and 80kmhr respectively.

[ProjectDirector]

Does anyone really think it’s a PITA to lock the CDL? I mean it’s not like you need to get off the couch to change the channel! Or out of the vehicle to lock the hubs! Hilarious.
...I love locking my CDL at every opportunity. It’s what makes it a Land Rover!

...now another can of worms :) ...at what max speed can you lock the CDL on the fly? And what’s the max speed you can drive with it locked? My rule of thumb has been 60kmhr and 80kmhr respectively.

Never been more than 80kmh only because didn't feel comfortable on that particular track and secondly I think any faster especially in unknown areas could be dangerous, the defender is not a WRX[emoji2]

[ozscott]

In my manual I have locked it at 100kph. No issues at all.

Cheers

[djam1]

80kmh will make the Tanami a looong drive

[weeds]

I have engage and disengaged anywhere up to 100km/hr

[trout1105]

I have always engaged/disengaged 4WD/CDL when stationary.
I know I CAN engage/disengage on the fly But I have never been a fan of doing that and it certainly can't do the transmission any harm doing this with the truck stopped.
I usually don't exceed 100kph on the dirt

[rangieman]

I have engage and disengaged anywhere up to 100km/hr
Yep same here [thumbsupbig]
Just wait for the long winded do`s and dont`s waiving brigade to pipe in [bigrolf]

[AK83]

On the fly or stopped makes no difference.
My only thing is not to engage/disengage whilst accelerating or slowing ... just in case.

LOL on the Tanami. The non-bitumen sections were wayyyy to rough (corrugations) to do more than about 60-ish when I was on it years back.

[The Cone of Silence]

I have ATBs in the front, centre and rear diffs and Dave Ashcroft maintains that the centre diff should still be locked anytime there's a chance of a wheel spinning for a prolonged period.

If it's good enough for Dave Ashcroft, it's good enough for me.

[jackdef90]

You may find the discussion "Pointless" and you have every right to think what you like on this matter But many here Do think that how the CDL is used on their landrovers IS worth discussing so your negativity isn't adding anything useful to the discussion at all.

As for starting a "Fist Fight" over this well I think that is a silly notion, None of us here want to start a third world war over ANY subject matter being discussed on the forum.
It may be that we have differing opinions on a range of subjects from time to time and that is a GOOD thing because many of us won't just accept things just because someone says it is 'Kosher" and follow along like Sheep, Isn't that one of the reasons why we own a Landrover in the first place [bigwhistle]

Obviously I wasn’t actually encouraging a fight. Go back to the disco forum.
Your rambling shows your age. Exactly what I’m talking about pointless comments like yours.
the thread has gone for 11 pages now and basically nothing has been decided just the same info regurgitated.

[DiscoMick]

I usually stop to engage mine. I know it can be done on the move, but I'm cautious.

[trout1105]

Obviously I wasn’t actually encouraging a fight. Go back to the disco forum.
Your rambling shows your age. Exactly what I’m talking about pointless comments like yours.
the thread has gone for 11 pages now and basically nothing has been decided just the same info regurgitated.

So Exactly How has either of your inane comments in this thread been of any use to the discussion?
Nothing will be "Decided" and set in stone here about how and when people engage their CDL because we all have different driving styles and BTW you rudeness is showing YOUR age.

[AK83]

This is why I stopped looking at this site. The pointless duscussions just drive me mad. Go and fist fight each other and be done with it


Obviously I wasn’t actually encouraging a fight. Go back to the disco forum.
Your rambling shows your age. Exactly what I’m talking about pointless comments like yours.
the thread has gone for 11 pages now and basically nothing has been decided just the same info regurgitated.

Seriously? [bighmmm]

Those two replies are your only contribution to the topic of CDL, one of which is to berate someone that has at least offered some input on the topic .. and you wonder why the thread is 11 pages of indecision!!

[jackdef90]

Seriously? [bighmmm]

Those two replies are your only contribution to the topic of CDL, one of which is to berate someone that has at least offered some input on the topic .. and you wonder why the thread is 11 pages of indecision!!

Actually the first post I made was in regard to the other argument that went on for two pages, where both parties were actually saying the same thing[bighmmm]

Then the second was in regard the pompous disco driver berating me for picking up on the fact that a lot of the topics turn in to a ****ing contest.

you want input here it is. Lock the cdl where there’s a chance of wheel spin.

[ozscott]

Is a pompous Disco driver worse than a pompous Defender driver?

[jackdef90]

Is a pompous Disco driver worse than a pompous Defender driver?

Geez mate don’t start this one,

[ozscott]

Haha. I'm kidding you.

Cheers

[Mick_Marsh]

The last time I engaged my CDL was when actioning a three point turn on a sealed road in an industrial estate.
I had to engage the rear axle as well.
Had I needed to deploy the winch, chops was winch bitch. Good job I didn't need to, hey chops?

[AK83]

I suppose another reason to engage CDL could be for the purpose of better grip for the handbrake?
The way I'm understanding the handbrake system is that even tho it's on the transmission(transfer case rear output), with the CDL unlocked it's really only a rear wheel/axle handbrake.

so if for example you're parked on a slippery surface, or excessive weight where the weight/grip combination is too much for a wheel/axle, with CDL unlocked that single wheel axle under load could slip, and the front axle isn't really helping.
Locking the centre diff then positively brings the front axle(or at least one wheel) into play.

I've only experienced one situation in my Rodeo where I had to park on a very steep incline, handbrake on, but both rears slipped as I tried to get out.
That is handbrake was doing it's job locking the rear wheels, just not enough grip at both rears to hold the car on the incline. Not massively steep, just looser gravel than I thought it was going to be.
Reason I had to stop was that I forgot to lock the front hubs.

Had to roll back about 20m to a less steep section of the track, handbrake (actually the wheels) held at that location, and I then locked the front hubs and continued onwards.

[tact]

[...]you want input here it is. Lock the cdl where there’s a chance of wheel spin.

Which is in the manual. And which pretty much all sides have advocated. This being the least contentious aspect of all - locking if there is any risk of wheelspin.

The rest is simple too - lock as soon as you leave tarmac - if that is what floats your boat.

[trout1105]

The manual also advises Not to engage the CDL on the run if there is any wheel slip and to back off the accelerator if this is the case, engaging/disengaging the CDL when stationary negates any risk of damage.

[1nando]

For those that believe a vehicle in true 4wd isnt a better handling vehicle please read the following;

4WD - Technical informations (http://rallycars.com/technical-stuff/full-time-4-wheel-drive-turbo-charged-cars/)

The best rally cars in the world have 3 diffs like the defender. The front is usually a open tye diff, the centre and rear diffs are torsen/atb type diffs. Now lets think about this;

If driving in true 4wd negatively effects vehicle handling why do these vehicles have torsen type diffs in the centre diff??

At high speed on a surface with less friction than that of tarmac loosing traction through a slipping wheel can lead to loss of vechile control. Its at this point the torsen centre diff locks and sends torque to both axles. As this happens the driver is now provided the abilty to control and drive the vehicle without potential loss of control.

Now; if a locked centre diff on a surface with less friction than that of tarmac on a strecth of road im not 100% familiar with is so bad to vehcile control as some have claimed to be BS, why do rally cars have torsen centre diffs???

Now some will claim; "im talking about compressed hard dirt blah blah blah". Now I've driven a few, actually a lot of dirt roads in my time which aren't my daily comute and even if they were the fact remains they're not sealed and are subject to erosion, weathering etc. Now the way i see it is that as soon as i get off the tarmac with my family onboard, all our gear and a truck weighing close to 3 ton do i care about the little extra transmission wear of having a locked centre diff? ??? FK no! My concern in vehicle control. I want to know i can throw the steering wheel to one side if needed, take evasive action and maintain vehcile control, vehicle control that a open centre diff can not offer.

Lock it or dont lock it, i dont care what you choose to do as its each individual's choice and vehcile. However to call bs on something thats true really does my head in. Defender is a true 4wd vehcile when locked, if you dont want to use it you should have bought a fiat panda!

[DefenderBrisbane]

Now I am not any sort of expert on this, but I think that locking the centre diff on unsealed surfaces is a good idea.

However, last year we took our Defender TD5 down the Strzeleki Track enroute to the Simpson desert. Because we here headed for the desert we had left our camper trailer at home and had gear on a roof rack. This was an oztent, spare wheel, tool box, spare parts, small gas bottle, two chairs and a few other little pieces so not a lot, the object being to keep the centre of gravity down.

We did notice the affect that this load had on vehicle stability. We also found it was more noticeable with the CDL engaged. I reckon it was because the additional traction made the vehicle grip ruts and other uneven bits and tend to track along them. So, we did some of the gravel road stages without the CDL engaged.

Anyone want to comment?

[1nando]

What you felt was a vehicle working with a tighter drivetrain, more traction and a **** load of weight on the roof! Someone will say transimisson "wind up". If your on a surface with less friction than that of tarmac like dirt then it is negligible; throw in cornering, ruts driven at speed and "wind up" is not an issue.

However had you hit a bad rut, corner or needed to take evasive action with the vehicle travelling at speed and with the cdl unlocked with all that weight on the roof then chances are you could have lost control and rolled the vehicle. You would be very unfortunate to lose control with the cdl locked under the same circumstances!

Ps: you should always try to load your vehcile with the lowest centre of gravity possible. The higher the centre of gravity the greater your chances are of rolling the vehicle.



Now I am not any sort of expert on this, but I think that locking the centre diff on unsealed surfaces is a good idea.

However, last year we took our Defender TD5 down the Strzeleki Track enroute to the Simpson desert. Because we here headed for the desert we had left our camper trailer at home and had gear on a roof rack. This was an oztent, spare wheel, tool box, spare parts, small gas bottle, two chairs and a few other little pieces so not a lot, the object being to keep the centre of gravity down.

We did notice the affect that this load had on vehicle stability. We also found it was more noticeable with the CDL engaged. I reckon it was because the additional traction made the vehicle grip ruts and other uneven bits and tend to track along them. So, we did some of the gravel road stages without the CDL engaged.

Anyone want to comment?

[Zeros]

Now I am not any sort of expert on this, but I think that locking the centre diff on unsealed surfaces is a good idea.

However, last year we took our Defender TD5 down the Strzeleki Track enroute to the Simpson desert. Because we here headed for the desert we had left our camper trailer at home and had gear on a roof rack. This was an oztent, spare wheel, tool box, spare parts, small gas bottle, two chairs and a few other little pieces so not a lot, the object being to keep the centre of gravity down.

Anyone want to comment?

Yes... far too much on your roofrack. That load is making the centre of gravity high! A gas bottle, toolbox and spare parts?? As well as spare wheel, tent, chairs and more. ...what no full jerry cans? LOL

All that steel! Not only top heavy, but potential missiles too.

Keep your fuel, tools, gas bottles low. Preferably your spare wheel too.

...and that stopped you locking your CDL on dirt!? Um...obviously somethings not right. Top heavy, swaying all over the road and reduced traction. Glad you didn’t have a blow out or hit a washout.

[tollchief]

I always found this video to be helpful. In the end it is your own choice, but it’s good in some situations and not others. Personally I’d love an ATB!

YouTube (https://m.youtube.com/watch?v=vFHCYuPTbfg)
thats rubbish about the centre diff blowing up if unlocked for more than 5 to 10 seconds differentiating, read the comments under the vid.
the diff lock was deleted in some markets.

[JoshV12345]

What about driving a fast dirt road, CDL locked, then coming to a cement dip/causeway, not so much the small ones but the longer ones, do you really need to unlock for that? Or even some dirt roads where they’ve put a bit of bitumen down for a short length but then changes back to dirt, especially on a really steep hill.

[weeds]

What about driving a fast dirt road, CDL locked, then coming to a cement dip/causeway, not so much the small ones but the longer ones, do you really need to unlock for that? Or even some dirt roads where they’ve put a bit of bitumen down for a short length but then changes back to dirt, especially on a really steep hill.

If I can see he end than I leave it locked...

[Zeros]

If I can see he end than I leave it locked...

agree. A short distance in a straight line should be ok.

[jon3950]

Unfortunately the best rally cars in the world are hamstrung by the regulations. Regulations have varied over the years but currently World Rally Cars run active (electronically controlled) centre diffs and passive (mechanical, torque biasing) front and rear diffs. If they had their choice, they would run active diffs front and rear as well.

I've been following this argument with some bemusement. There's a reason we can't all agree on whether to lock the centre diff or not and that's because there's no one right answer. In some conditions a locked diff will be a compromise, as will an unlocked diff. That is why active diffs were developed, they constantly vary the amount of lock-up to suit the conditions. Those of you who have a driven a D4 on the dirt will appreciate how well they handle - the centre diff is part of this.

Dirt road conditions vary greatly, some have high levels of grip, some don't, and to say you should always have your diff locked or unlocked won't be the best answer for all conditions. Then there's the vehicle itself, wheel base, weight distribution, available power, not to mention the speed you're travelling at. Suddenly there's an awful lot of variables to contend with.

Broadly speaking, a locked centre diff will make the car feel more planted on the road and provide higher levels of grip - in a straight line. It also makes it more reluctant to turn in. Here's where comparing a Defender to a rally car is a little unfair. A rally car has better suspension and has more power available, so you can move it around on the road and unsettle it to make it turn in. Where 4wd rally cars have a big advantage over 2wd is speed out of corners, as the high levels of grip enable you to put more power to the ground, rather than speed into and through a corner.

The best suggestion I can make is to feel what your car is doing and how it is interacting with the road. There will be some circumstances where locking the diff is beneficial, others where it isn't. And there'll be plenty in a Defender where it makes stuff all difference. I've found it makes less of a difference in the Defender than it did in the D1 or D2, but I would expect it would make a bigger difference in a 90 than my 110 and even less in a 130.

Also I think this talk of destroying centre diffs is a bit of a furphy. This is a problem in snow or muddy conditions, or off-road where traction can be completely lost on one wheel, causing significant differential rotational speeds between front and rear. I'm not convinced this would happen on your average dirt road drive.

Cheers,
Jon

[tact]

For those that believe a vehicle in true 4wd isnt a better handling vehicle please read the following;

4WD - Technical informations (http://rallycars.com/technical-stuff/full-time-4-wheel-drive-turbo-charged-cars/)

The best rally cars in the world have 3 diffs like the defender. The front is usually a open tye diff, the centre and rear diffs are torsen/atb type diffs. Now lets think about this;

If driving in true 4wd negatively effects vehicle handling why do these vehicles have torsen type diffs in the centre diff??

Ohhhhh, ummmmm let me guess.....Is it because ATB's allow differentiation completely NOT like a locked centre diff? Your point above doesn't work well for supporting your argument.



[...] loosing traction through a slipping wheel can lead to loss of vechile control. [B]Its at this point the torsen centre diff locks and sends torque to both axles.

Don't let these facts get in your way...
- ATB's in and of themselves don't EVER provide a complete lockup. Never. Thats right, never ever. (ref your words in bold above claiming they do " lock and send drive to both axles"). ATB's allow differentiation, always. ATB's resist (not stop completely a'la locked up) excessive differentiation up to a point. Once a wheel has lost all traction an ATB is as useless as an open diff. Which brings me to my next comment...

- ATB's, in the instance you seem so worried about - a wheel in the air at speed down a hard packed (or loose) road ... will behave exactly like an OPEN diff.
- in a more real scenario, like how I drive on dirt roads with all 4 wheels on the deck, an ATB is far from being a locked diff!

So in short - if rally cars with ATB's are your poster boy for things like stability and safety and performance on dirt roads - because in your mind you equate them to your vehicle with the CDL locked..... you are way off track. ATB's do improve stability and safety on fast loose stuff - but it is because they are NOT by any measure like a locked centre diff.

ATBs are also better than an open diff because they allow differentiation always, like an open diff, unlike a diff lock - but ATBs are much better than open diffs at controlling the differentiation they allow up to a point. (i.e. Until traction at one wheel is completely lost).

The reason rally cars run ATB's is exactly what I argue - they allow differentiation front/rear and left/right. Completely unlike when your CDL is locked.

(The better rally setups have electronic controls that control the amount of front/rear differentiation from none to full locked - because on occasion there is a place for having a diff locked. Heck, even the Ashcroft ATB replacement for centre diff on Defenders can still be locked just like the original open centre diff - when its needed.)

[raffynn]

Fully agree with Rick, never lock it on normal dirt road driving, vehicle (130) handles more than adequately, (whilst an intentional drift here and there is always a possibility, I am not in a rally) never had a problem with the CD. Cheers Rafferty

[1nando]

I really can't be bothered sharing any more videos and facts. If you want to drive your 4wd with a unlocked cdl on a dirt road then all power to you. If ever you are unlucky enough to loose control and drift into a tree think of me and the how the situation could have been avoided so easily. [emoji6]

[Zeros]

Locking the CDL in a Land Rover is one of life’s great simple pleasures.

The figure 8 gate is as much a design classic as the Defender itself.

It’s Easy. Straightforward. Perfect. and uniquely Land Rover.

Why wouldn’t you lock the CDL at every chance you get?

[Ancient Mariner]

If anyone feels they lack the experience or skills to drive a gravel road without a security blanket lock the center diff by allmeans.Me I have faith in Mr Quaife[biggrin]




AM

[dazzler]

Locking the CDL in a Land Rover is one of life’s great simple pleasures.

The figure 8 gate is as much a design classic as the Defender itself.

It’s Easy. Straightforward. Perfect. and uniquely Land Rover.

Why wouldn’t you lock the CDL at every chance you get?


...if you have an ATB in the middle like me :P should be keeping my head down really....
pd

[Zeros]

...if you have an ATB in the middle like me :P should be keeping my head down really....
pd

😎 Even with an ATB, the ability to lock the CDL defines a Land Rover.

[AK83]

I really can't be bothered sharing any more videos and facts. If you want to drive your 4wd with a unlocked cdl on a dirt road then all power to you. If ever you are unlucky enough to loose control and drift into a tree think of me and the how the situation could have been avoided so easily. [emoji6]

I think some perspective should be made of this particular comment.

What you've implied with that reply is that a driver of any vehicle on gravel roads is safe if it has a solidly locked 50:50 power transfer front and rear that you will not 'drift into a tree'? No matter how ignorant this driver may be! Common sense need not apply here, and they enter into those situations at any speed no matter how stupid the speed ! i.e .. a 4WD with solidly locked drive front:rear will save them from monumental stupidity :confused:


Interesting advice![tonguewink]

[1nando]

I think some perspective should be made of this particular comment.

What you've implied with that reply is that a driver of any vehicle on gravel roads is safe if it has a solidly locked 50:50 power transfer front and rear that you will not 'drift into a tree'? No matter how ignorant this driver may be! Common sense need not apply here, and they enter into those situations at any speed no matter how stupid the speed ! i.e .. a 4WD with solidly locked drive front:rear will save them from monumental stupidity :confused:


Interesting advice![tonguewink]

Who mentioned locking the front and rear, is that what you mean by your last statement or are you implying locking the centre diff distributes torque 50/50 front and rear?

Fyi i had a ashcroft centre atb, elockers front and rear and a complete ashcroft/maxi drive drivetrain. Every single part of my drive train you could imagine was HD as i used it for what i built it for.

Before getting my centre atb i would always lock the centre diff on these so called "hard dirt" roads. I didnt bother once i got the atb in the centre and thats why i bought it.

The issue here is what constitutes a surface that does not provide enough friction to ensure wheel spin does no occur. Now i think of it like this; on many trips/4wd days on "hard dirt" i can only say that on a number of occassions on steep sections i have slipped where my joggers have not been able to provide me enough grip. I think we have all witnessed someone slip on a dirt hill, would this same person slip on a sealed road of the same gradient, i highly doubt it. A dirt road will never have the friction of a tarmac road, is more likely to suffer erosion, areas of very light/maybe bull dust etc making it even less stable. Theres also the fact that you wont know what condition the road is in so I've learnt to always prepare for the worst and hope for the best.

Now for the record im a professional driver which does not in any way imply that you should take my word as gospel but i pride myself on not ever having lost demerit points or being in an accident, ive also done a lot of advanced driving courses and raced a 1000c cbr. I also take unsealed road driving seriously especially if my family is on board. Before my centre atb i would lock the cdl without failure on a unsealed road. I posted a clip earlier in this thread highlighting the difference between a vehicle locked in true 4wd and one that is not on a skid pan. This video was done Andrew st Pierre whos opinion on Toyota is questionable in my eyes but has excellent overland/touring advice and has probably done more kms than anyone on this thread through different countries and continents and whos opinion on the subject at hand i respect. Hes been there and done what i could only dream of doing.
Now some on here siad that this didint apply to the defender as its a permanent 4wd system. The video clearly shows the vehcile in true 4wd even when its towing the camper maintain control and there is no situation. True 4wd allows you to drive through a corner with confidence and control.

I own a brsnd new y62 patrol. It has some excellent technology (what else would you expect from the same company that built "godzilla" otherwise known as the GTR). i still put the thing in true 4wd on dirt. It weighs 3 ton and it loves a drift a bit like its smaller cousin the nissan silvia when its not and left to the technology do its thing. True 4wd keeps the vehcile stable, allows me to power out of a corner and is just confidence inspiring.

But eh....ive posted 2 videos and facts for people to read and yrt no ome has produced evidence to the contrary, just their "expert" opinion [emoji8]

[87County]

Wow, this thread has sure aroused some passionate views !

I guess it all could be summarised with a statement like "in circumstances which may allow substantial front/rear differential action, intelligent engagement of the cdl should be considered" ?

[bighmmm] ducks for cover

[weeds]

Soooo what has the OP decided on??

[ozscott]

Or if you just like the feel of the diff lock being applied.... Hi my name is Oz and I'm a diff locking junkie... and I like gadgets... I haven't locked my centre diff in 3 days now

Cheers (oops)

[ProjectDirector]

Soooo what has the OP decided on??

Phew [emoji28] , I am the OP.
My original question was purely to get drivers' opinion whether they lock CDL on hard smooth/compacted dirt roads and if there was a risk of windup.

I thought I will 'open a can of worms' but not to this level.

Question answered, CDL locked on dirt

I have been driving mainly Toyotas for the company I worked for many years, stringing up tower lines in bush and we were always taught to lock hubs and 4wd on dirt roads.

I thought the same applied for defender but given the transmission windup possibility made me ask the question anyway.

Cheers everyone and thank you for your responses.

[B.S.F.]

All this has been very helpful. It convinced me that driverless cars are a good thing.
.W.

[weeds]

Finally.....an end to the discussion

[1nando]

Phew [emoji28] , I am the OP.
My original question was purely to get drivers' opinion whether they lock CDL on hard smooth/compacted dirt roads and if there was a risk of windup.

I thought I will 'open a can of worms' but not to this level.

Question answered, CDL locked on dirt

I have been driving mainly Toyotas for the company I worked for many years, stringing up tower lines in bush and we were always taught to lock hubs and 4wd on dirt roads.

I thought the same applied for defender but given the transmission windup possibility made me ask the question anyway.

Cheers everyone and thank you for your responses.You were taught that becuase from a legal and liability stand point they would have to advice the safest method for travelling dirt roads. If you had not been told to use the 4wd system and lost control causing you serious harm and or death they could be sued I'd imagine.

[ProjectDirector]

You were taught that becuase from a legal and liability stand point they would have to advice the safest method for travelling dirt roads. If you had not been told to use the 4wd system and lost control causing you serious harm and or death they could be sued I'd imagine.

I would agree with you to some extent and very true especially current days. But...

Last Tuesday I went to Craig's Hut (Mt Buller Victoria for those not in Vic) and got on to Circuit Rd track and decided to lock centre diff soon as I left the bitumen.
This track is well maintained and most part of it was regraded in time for snow season.

Large section of it was smooth and compacted and immediately thought, should I or not?
My instinct told me keep it locked and sure enough as I was driving (40-60kmh as there are lots of turns) a lot of wet sections appeared. I doubt I would have time to engage cdl and save myself from any embarrassment or accident. The defender handled it very nicely.

Cheers

[bee utey]

Locking CDL on dirt is like paying your insurance premium. Most careful drivers will never lodge a claim, some live happily ever after CDL saves their hides. Whatever locks your boat. [smilebigeye]

[Xtreme]

I would agree with you to some extent and very true especially current days. But...

Last Tuesday I went to Craig's Hut (Mt Buller Victoria for those not in Vic) and got on to Circuit Rd track and decided to lock centre diff soon as I left the bitumen.
This track is well maintained and most part of it was regraded in time for snow season.

Large section of it was smooth and compacted and immediately thought, should I or not?
My instinct told me keep it locked and sure enough as I was driving (40-60kmh as there are lots of turns) a lot of wet sections appeared. I doubt I would have time to engage cdl and save myself from any embarrassment or accident. The defender handled it very nicely.

Cheers

That red clay that they have brought in and are using on more than the circuit road packs down well and gives a nice smooth surface but is extremely slippery when wet and it doesn't dry out very quickly. I was there a few weeks ago and know exactly what you mean.

[rangieman]

Soooo what has the OP decided on??
Might just be in the fetal position under the table crying [bigrolf]

[tact]

Before getting my centre atb i would always lock the centre diff on these so called "hard dirt" roads. I didnt bother once i got the atb in the centre and thats why i bought it.


Glad you now know that was unwise... (not bothering to lock your CDL when you had one with an ATB in it).

You're welcome! Given through my efforts and persistence against all odds and insults - you now are well aware that: if you were tootling along a dirt road and struck some slippery bit that could easily be so slippery that your ATB would have also behaved like it was an open diff .... and sent you up that tree you worry about me hitting. (Where is that tree? Chainsaw is ready to go!) [bigwhistle]

Looking on the bright side... you survived all those long drives with your ATB unlocked, perilous as you believe that (a diff that behaves as if open when things have turned to custard) may be!




[...]
Now some on here siad that this didint apply to the defender as its a permanent 4wd system. The video clearly shows the vehcile in true 4wd even when its towing the camper maintain control and there is no situation. True 4wd allows you to drive through a corner with confidence and control.

Still persisting with the "full time 4x4 isn't true 4x4 with CDL open. Lock the CDL and there it is - true 4x4"

You haven't given one of my suggestions a try have you. The one about jacking up a wheel on the front axle, and one on the back as well, lock your CDL.... and try to drive your "true 4x4". How true is it?

No hard feelings re your comments about losing respect for me. I still care enough about you to write:
"Y'all remember now, lock your centre diff even if its got an ATB centre - just cannot trust them when a wheel loses all traction!"

[County4.4]

My 2 cents worth.
I did a trip out west past ceduna surfing fishing last year.
Did lots of beach driving chasing mulloway, sometimes 30km up the beach or more and then back over a couple of weeks.
I rarely locked the cdl (in my ignorance ???) to prove to my mate in his 80 series toyota how good defenders are on the beach.
On the 20 hour drive home to melbourne i noticed how much louder and whining my transfer case was.
Coincidence ??
Now I always lock the cdl with my new transfer case.

[1nando]

Glad you now know that was unwise... (not bothering to lock your CDL when you had one with an ATB in it).

You're welcome! Given through my efforts and persistence against all odds and insults - you now are well aware that: if you were tootling along a dirt road and struck some slippery bit that could easily be so slippery that your ATB would have also behaved like it was an open diff .... and sent you up that tree you worry about me hitting. (Where is that tree? Chainsaw is ready to go!) [bigwhistle]

Looking on the bright side... you survived all those long drives with your ATB unlocked, perilous as you believe that (a diff that behaves as if open when things have turned to custard) may be!




Still persisting with the "full time 4x4 isn't true 4x4 with CDL open. Lock the CDL and there it is - true 4x4"

You haven't given one of my suggestions a try have you. The one about jacking up a wheel on the front axle, and one on the back as well, lock your CDL.... and try to drive your "true 4x4". How true is it?

No hard feelings re your comments about losing respect for me. I still care enough about you to write:
"Y'all remember now, lock your centre diff even if its got an ATB centre - just cannot trust them when a wheel loses all traction!"[emoji848]https://youtu.be/gwm_-SA8jlQ

YouTube (https://youtu.be/EBmw6Wpfe6M)

Once more. The first minute clearly says it all

[AK83]

Who mentioned locking the front and rear, is that what you mean by your last statement or are you implying locking the centre diff distributes torque 50/50 front and rear?
......

:confused:
Who made the claim that locking a diff doesn't give you 50:50 torque across it?
I'm thinking you're confused as to what some replies were describing!
I was the one with the RRC tow starting the 8ton truck on gravel driveway where I did get 50:50(ish) drive front:rear when I had 1 front(LHS) and 1 rear(RHS) spinning for a short time before they gripped and the RRC with all open diffs started to pull the 8ton truck.


Phew [emoji28] , I am the OP.
....
I thought the same applied for defender but given the transmission windup possibility made me ask the question anyway.
.....

It shouldn't produce transmission windup.
But as mentioned by others, and as I've experienced with my part time 4WDs, you can experience more understeer in some situations.
TBH, I now lock the CDL on fast dirt in my D1(where I never did in my RRC) but don't really feel any excessive understeer(like my part time 4WDs gave the feeling of).

[tact]

[emoji848]https://youtu.be/gwm_-SA8jlQ

YouTube (https://youtu.be/EBmw6Wpfe6M)

Once more. The first minute clearly says it all


In summary the first minute says engage 4wd as soon as you leave the tarmac for safety as 4wd is safer than 2wd on dirt roads.

Agree wholeheartedly that all part time 4wd owners such as yourself should get out of the vehicle if necessary to lock hubs, and shift that lever or dial from 2Hi to 4Hi. Much safer than 2wd. Do it.

Owners of full time 4wd vehicles are in 4wd on road and off-road already. No need, not even a means to, shift out of 2wd. (By all means lock that centre diff though whenever there is a chance of wheelspin - or earlier if you so desire.)

Where there is any contention at all is that you have embarked on a rather ill informed mission that preaches incorrectly that:
- an all wheel drive with centre diff open isn’t a “true 4wd” because one wheel spinning means no drive
- with centre diff open only the front or rear wheels can be driven(!?? So wrong!)
- gotta lock that CDL to then be in “true 4wd”
- (which of course sets up the driveline just like a part time 4x4 in 4Hi or 4Lo - I.e. front and rear drive shafts are locked together)
- locked CDL is “true 4wd”, unlocked isn’t, despite the fact that crossaxled (ie two wheel spinning wheels) will see your “true 4wd” with no drive either. Why aren’t the other two wheels driving?
(All debate to date setting aside assists like TC etc)

Along the way scrambling to support the unsupportable (above) you have revealed a deep misunderstanding of ATBs. Misplaced trust for sure- Demonstrated by your “not bothering to lock CDL with an ATB fitted”. Not realising that on open dirt roads the confidence an ATB gives when things are within the ATBs constraints - can lead to disaster when a wheel, any wheel, does wheelspin and the ATB suddenly behaves like an open diff... and you are driving faster than you might have been otherwise.

The “true 4wd” assertions you make regarding vehicles with front and rear driveshafts locked are unsupportable. It takes technology like ABS/TC or diff locks in front & rear axles to make a vehicle you label as “true 4wd” actually come close to being able to drive all 4 wheels all the time.

In practice, on that fast dirt road, your “true 4wd” (without other tech) will be able to slip, or spin up, a front and/or a rear wheel.

There sure are times when having the CDL locked, on fast dirt roads, is a must. Eg I have have driven very loose scree dirt roads where the stones are like ball bearings. With CDL open any sudden movement of the throttle, anything less than intensely delicate throttle handling, would see revs rise out of proportion to forward travel (wheel spin starting). So I lock the CDL. (The “any chance of wheelspin” postulation).

As others suggest sometimes it’s good to lock the CDL just for the sake of it, using the mechanism to keep it functional etc. I do that too.

[rangieman]

Something appropriate [bigwhistle]
140130

[PhilipA]

I would like to add my 10c worth.

I have a 2002 D2 which I fitted with a CDL and previously owned 2x RRC with LT95 and one RRC with Borg Warner (BW.)

It is a lot easier to start on dry sand with the CDL engaged than with a BW as the BW acts as an open diff until it gets "over the hump". I always found that the first 10 metres were a struggle.

I used the D2 on sand before CDL on a sand training day at Stockton and had enormous TC intervention particularly on long slopes. Once I had the CDL , I have never really tried to start on dry sand without it . I went up to Rainbow beach last year and was amazed how easily the D2 started on dry sand at the Northern exit to the corduroy track.

I don't use CDL on wet sand at low tide until I need it to cross dry sand on the beach exits. I have never had TC come on on wet sand at Rainbow. Stockton is a different matter. I don't go near the wet sand there as it is treacherous.

I agree that the CDL is desirable on loose straight dirt roads. However I did the GRR towing my 1000KG camper before I fitted the CDL and when I dismantled the LT230 , the diff shims were in excellent condition at about 180KK. So Ashcroft may be talking Britain where everything is muddy and slippery.
Last week I visited Yarrangobilly caves where the exit and entry tracks are firm but corrugated dirt with many hairpins. I didn't lock the CDL and traction control only activated once on the corrugated exit of a hairpin.
I consider that the stresses from drivetrain windup when traversing very twisty firm tracks are IMHO more than the stresses induced by any wheelspin so I don't lock the CDL in these circumstances. If you have grippy tyres the windup is pretty extreme .

Finally I also think that lubrication plays a role in centre diff failure. To get my CDL nose I bought a dismantled LT230 with CDL with AFAIR a reported 240KK on it. It had reportedly not been off road. However the diff shims were gone just about completely and there was a tonne of swarf in the little sump below the Diff.

You must avoid wheelspin at all costs. There used to be a bloke in a club I was in who used to go through axle diffs all the time. While he probably had his CDL locked in his D1 he used to sit at obstacles spinning wheels and the axle diff shims used to grab and seize.

Regards Philip A

[donh54]

Glad I survived all that dirt road driving I did BEFORE I got a 4wd! Mini Mokes, Vanguards and various MOWOG products, not one of which was 4wd, or had a CDL! Learnt very early on to read the conditions and drive accordingly. Just like I still do! [biggrin]

[tact]

Glad I survived all that dirt road driving I did BEFORE I got a 4wd! Mini Mokes, Vanguards and various MOWOG products, not one of which was 4wd, or had a CDL! Learnt very early on to read the conditions and drive accordingly. Just like I still do! [biggrin]

Lucky to be alive! [bigrolf]

(At least you were under no illusions that your moke was a "true" front wheel drive and therefore inherently safer than it truly was...) :soapbox:

[strangy]

I’m not sure what to do now.
Is there a risk of inadvertent air bag deployment by over usage of the CDL or could it be the other way around?
When I engaged the CDL last time my passenger started to whine and I was concerned as didn’t want to experience driver wind up from CDL overuse.
Looking back I think that not using the CDL when I should have may have contributed to radio stations being out of reception earlier than when CDL wasn’t engaged.
I’ve fixed a few of these things but am still unsure if the CDL may be contributing to the wear on the shift lever knob.
I’m also concerned that uni joints will wear prematurely.
Maybe this is affecting my overall aging process too.
Any help greatly appreciated.[emoji57]

[tact]

[...]passenger started to whine [...]driver wind up from CDL overuse.[...]

:TakeABow: that made my day! [bigrolf]

Time I lightened up!

[rangieman]

I’m not sure what to do now.
Is there a risk of inadvertent air bag deployment by over usage of the CDL or could it be the other way around?
When I engaged the CDL last time my passenger started to whine and I was concerned as didn’t want to experience driver wind up from CDL overuse.
Looking back I think that not using the CDL when I should have may have contributed to radio stations being out of reception earlier than when CDL wasn’t engaged.
I’ve fixed a few of these things but am still unsure if the CDL may be contributing to the wear on the shift lever knob.
I’m also concerned that uni joints will wear prematurely.
Maybe this is affecting my overall aging process too.
Any help greatly appreciated.[emoji57]
Really :wallbash:
Don`t add more fuel to the fire FFS:bangin:

[cripesamighty]

Strangy. That's funny. I love the 'wear on the shift lever knob' bit. Sarcasm par excellence...

[Tins]

Amazing thread. I am reminded of one where I took a position on mechanical advantage. Pretty much everyone who posted was saying the same thing, but apparently I was speaking Klingon.

The OP was concerned about windup, IIRC. Here's a test. Your car will have a 4WD light of some kind. Engage the CDL in the manner you describe. Drive the car on the roads/tracks you encounter. When you get back to the bitumen, disengage the CDL. Watch to see when the light goes out. Perhaps you could accel/decel, or steer left and right a bit. If the light doesn't go out you have windup. Stop and reverse a little. If it doesn't go out then you have windup to be concerned about.

I am in the camp of engage CDL on loose surfaces. In my D1 it seems to stabilise the car. When I was driving my D2 I don't think I bothered, but the D2 was always more stable in a general sense ( it's been some time since I drove my D2 ). However, as someone else said, if it is good enough for Dave Ashcroft, it's good enough for me.

Another thing I would say: if a thread becomes boring to individuals, I would ask; why are you reading it? Even more, why are you contributing ( or not )? It makes no sense. Move on.

[Tins]

Really :wallbash:
Don`t add more fuel to the fire FFS:bangin:

Actually, Chris, I reckon Strangy nailed it. No /sarc tag required.

[1nando]

" Another example of where the ATB would help would be when rapidly changing from high to low traction surfaces, *i.e. when driving on snow or ice,

In both of these examples the ATB will limit the amount the difference in propshaft speed and transfer torque to the axle with traction.

The two big advantages are increased traction when unlocked and eliminating the weakness of the stock unlocked centre diff." Ashcroft


Thats what an atb does in the centre diff. So yes i didnt have to lock the centre diff as the atb would automatically transfer torque to the axle with the most traction or least propshaft speed. In other words drive would be sent to the axle that had no wheels spinning or the least propshaft speed. This is safer than using the standard cdl unlocked and a good compromise between high traction and low traction surfaces. To the average Joe locking the centre diff on dirt is just playing it safe.

You dont have to agree and I dont want anyone to agree for the sake of it, simply my opinion. However i bought a 4wd to transport me and my faimly safely to places. Never had an issue with a locked cdl, never lost vehicle control never understeered as some claim and the "wind up" issue was so bad that i dont know how the car didnt blow up...not!

The problem at hand is what constitues a high traction surafce and i argue that anything that is not a man made covered surface will be lower traction hence engaging true 4wd is the safest bet.

Andrew st Pierre recomends it, Bruce Davis recomends it, 4x4 Australia recomends it...but eh....people on this forum seem to know better.

I had to sell the 110 to buy a family friendly vehicle so i bought a Patrol. I put it in 4wd every time it touches the dirt or any surface with less traction than that of a man made surface like i did the 110. I just dont know why i havent "understeered" into a tree or lost control.....the other thing i dont understand is how all this wind up hasnt ever blown up my drive train on any vehicle???? Its got me puzzled; 🤣🤣🤣🤣not! If there was ever going to be a vehicle where wind up was an issue the independent y62 with 400hp and weighing 3 tons would be it.....

What i have seen is the result of people loosing control of their vehicle when they've lost traction or encountered unexpected terrain. Kind of going to happen when your on dirt road with no guarantee of surface quality. You learn to apprecaite surface quality when you ride motorbikes, even more so when u come off them.

Ps: the definiton of insanity is correct! [emoji14] so one more video. The first 4 minutes say it all and from 10 minutes also! Enjoy
YouTube (https://youtu.be/TOweeVYkyps)

[tact]

" Another example of where the ATB would help would be when rapidly changing from high to low traction surfaces, *i.e. when driving on snow or ice,

In both of these examples the ATB will limit the amount the difference in propshaft speed and transfer torque to the axle with traction.

The two big advantages are increased traction when unlocked and eliminating the weakness of the stock unlocked centre diff." Ashcroft.

All the above is correct. But as always “a text without a context is a pretext”.

The context for those remarks (found elsewhere in the same Ashcroft web page) is that all the above is correct “within certain limits” of the ATB to function as above.

That limitation is regards when one wheel (or one prop shaft, in respect to centre diff) can spin up way more then the other side.

My points stand. You could easily spin up a front and/or a rear wheel with centre ATB unlocked. The ATB action falls away to behave like an open diff.

The amazing thing thing is that the ATB action works just as well when wheels on BOTH sides are on ice, or BOTH sides are on tarmac. Ie a rear axle with ATB will handle both rear wheels being on ice. But when one is on tarmac/rock/gravel and the other is on ice - game over. The difference in available traction across the device means it functions only as an open diff.

By your logic - you may we’ll be lucky to be alive driving dirt roads with an unlocked centre ATB! Because if things turned to custard, an off camber bend, slightly uphill, a little rut your inside front wheel traverses and loses all traction. Your pro reflexes dulled or distracted a moment .... that front wheel, wheelspins up. Your ATB says “I’m a teapot!”

You are then then as much a dead duck as you think the poor folks with just an unlocked OPEN diff would be in that situation.

Your videos still do not address these simple facts. Apples and oranges. Pretexts without context.

[donh54]

Beats me how people like Len Beadell survived opening up the country they did, with nowt but a Series 1 or 2 Landy, with no CDL, and open diffs. Traction must've been different back then

[trout1105]

Beats me how people like Len Beadell survived opening up the country they did, with nowt but a Series 1 or 2 Landy, with no CDL, and open diffs. Traction must've been different back then

Those days they didn't have to worry about buggering up the CDL because they didn't have one.
The Main reason why I lock my CDL on the loose stuff is to prevent destroying it, The added handling/traction is just a bonus [thumbsupbig]

[DiscoMick]

I guess an ATB plus TC to stop wheels spinning would be a very effective combination.

[harro]

Beats me how people like Len Beadell survived opening up the country they did, with nowt but a Series 1 or 2 Landy, with no CDL, and open diffs. Traction must've been different back then

And probably a very well used shovel[bighmmm]

[tact]

Beats me how people like Len Beadell survived opening up the country they did, with nowt but a Series 1 or 2 Landy, with no CDL, and open diffs. Traction must've been different back then


And probably a very well used shovel[bighmmm]

Well used shovels never lasted as long as my grandfather's axe. [bigwhistle]

[Tins]

Beats me how people like Len Beadell survived opening up the country they did, with nowt but a Series 1 or 2 Landy, with no CDL, and open diffs. Traction must've been different back then

If you have listened to Len's wonderful and often hilarious speech, you'd know that he spent a lot of his time bogged, and that most of the time he had over half a dozen Series vehicles at his disposal. Imagine what he could have achieved with a CDL equipped D2.

[DiscoMick]

Didn't he also have a dozer to drag him out of bogs?

[AK83]

If you have listened to Len's wonderful and often hilarious speech.....

Never heard the speech, but read the 'Bush' book collection.
My lasting impression of those tales was relentless 'repairing of tyres every day and night', and 'eating tinned beef and dry biscuits'

[dennisS1]

I will start by saying that everyone can drive their Land Rover the way they wish, But why you would think that driving down a grave/ sand road at 80 to 100 Kmh in a straight line that all of the wheels are not turning at the same speed is beyond me. Yes, every time we turn there is a slight difference between left and right / back and front but that’s what the Diffs (all 3) are there for.
As for drive feel / control I would much prefer the feel of the CDL working the way it was meant for rather than locked up. As I stated in my first post never over 40Km/h and only when wheel spin is likely.
Dennis

[Tins]

Never heard the speech, but read the 'Bush' book collection.
My lasting impression of those tales was relentless 'repairing of tyres every day and night', and 'eating tinned beef and dry biscuits'

It is worth the effort. His family have put it up as a pay to own thing. I heard it first on a trip, from a cassette tape. I could never get the bloke who had the tape to make me a copy. Len is brilliant, and funny. I will try to find the link. You will need to pay, but so what.

[Tins]

I think you will find links to Len's speech here. Give the blokes family a $ or two, and laugh: His stories are worth the price of admission.

Our products (http://www.beadell.com.au/our-products.html)

[donh54]

I think you will find links to Len's speech here. Give the blokes family a $ or two, and laugh: His stories are worth the price of admission.

Our products (http://www.beadell.com.au/our-products.html)I've read his books and heard parts of his speech. I'll gladly pay for the full speech. Thanks for the link!

[Zeros]

If anyone is still in doubt about locking the CDL as often as possible (ie whenever off tarmac), watch this video. Land Rover Defender Talk. Andrew St Pierre and John RIch - YouTube (https://m.youtube.com/watch?v=FnxVfm9I-XQ)

Also, IMO, it might help to think about the Defender 4x4 system a little differently. Instead of seeing it as an on-road system that can be occasionally locked up for off-road Think about it the other way round. ...Defenders are primarily off road vehicles. As such, the CDL is designed to be locked all the time. Unlocking it simply enables you to drive on bitumen without causing transmission wind up. So leave the CDL locked, unless you need to drive on the tarmac/bitumen. Simple.

Roof loads? It’s an absolute no brainer to keep weight low. A roof rack is for a wet swag, perhaps a second spare tyre if on an extended overland trip and collecting firewood close to camp. Keep all other heavy objects such as tools, fuel, gas bottles, water, etc off the roof. Pack lighter. It’s too dangerous to be top heavy.

[ProjectDirector]

If anyone is still in doubt about locking the CDL as often as possible (ie whenever off tarmac), watch this video. Land Rover Defender Talk. Andrew St Pierre and John RIch - YouTube (https://m.youtube.com/watch?v=FnxVfm9I-XQ)

Also, IMO, it might help to think about the Defender 4x4 system a little differently. Instead of seeing it as an on-road system that can be occasionally locked up for off-road Think about it the other way round. ...Defenders are primarily off road vehicles. As such, the CDL is designed to be locked all the time. Unlocking it simply enables you to drive on bitumen without causing transmission wind up. So leave the CDL locked, unless you need to drive on the tarmac/bitumen. Simple.

Roof loads? It’s an absolute no brainer to keep weight low. A roof rack is for a wet swag, perhaps a second spare tyre if on an extended overland trip and collecting firewood close to camp. Keep all other heavy objects such as tools, fuel, gas bottles, water, etc off the roof. Pack lighter. It’s too dangerous to be top heavy.

Couldn't agree more with you on both subjects[emoji106]

When I go camping it's usually 3 of us, so the sleeping bags and self inflating mattresses and the 6kg tents are the only items on the roof rack.

[ozscott]

We are off topic but I agree about the weight. Having said that on big trips without a trailer or boat I use the roof and it's max handbook weight limit. An advantage of diesel is that you can legally put a Jerry of the stinky stuff on the rear bar. You can't with petrol. So.for me 24 litres in a low profile fat boat tote tank goes on the roof as the only place for it. My instant up tent, one piece fishing rods, recovery tracks etc go up too. I found any extra top heaviness was well and truly mitigated by better tyres and Bilstein shocks with good springs (the 2 inch lift did not hurt handling) and thousands of miles on dirt roads with this set up proved to be stress free.

Cheers

[DiscoMick]

Is your roof limit 75kg?

[weeds]

Is your roof limit 75kg?

Ya don’t want to know what my roof load weighed when I did the Simpson.

[1nando]

If anyone is still in doubt about locking the CDL as often as possible (ie whenever off tarmac), watch this video. Land Rover Defender Talk. Andrew St Pierre and John RIch - YouTube (https://m.youtube.com/watch?v=FnxVfm9I-XQ)

Also, IMO, it might help to think about the Defender 4x4 system a little differently. Instead of seeing it as an on-road system that can be occasionally locked up for off-road Think about it the other way round. ...Defenders are primarily off road vehicles. As such, the CDL is designed to be locked all the time. Unlocking it simply enables you to drive on bitumen without causing transmission wind up. So leave the CDL locked, unless you need to drive on the tarmac/bitumen. Simple.

Roof loads? It’s an absolute no brainer to keep weight low. A roof rack is for a wet swag, perhaps a second spare tyre if on an extended overland trip and collecting firewood close to camp. Keep all other heavy objects such as tools, fuel, gas bottles, water, etc off the roof. Pack lighter. It’s too dangerous to be top heavy.Puma defender has a 150kg load rating. Off topic but thats the LR rating.

Zeros mate; you are not allowed to post facts, vdeos and links to litreture as this forum loves to operate on ignorance and bs.....and then call the pople that actually post facts up to be the ones talking BS.

Good video. Im sure someone will be more experienced than Andrew and Rich and say its non sense. Of course its not as safe, the understeer, the wind up.......[emoji85]

Written by Tact;
"The amazing thing thing is that the ATB action works just as well when wheels on BOTH sides are on ice, or BOTH sides are on tarmac. Ie a rear axle with ATB will handle both rear wheels being on ice. But when one is on tarmac/rock/gravel and the other is on ice - game over. The difference in available traction across the device means it functions only as an open diff. "
When you said the above you obviously did not read the rally post on torsen/atb type diffs i posted earlier and how they work on a centre diff, did you?? Clearly did not!

Tact out of curiosity do you have a atb in your centre diff? I know you have them on your front and rear but not sure about your centre diff.

I did. Let me tell you any prop shaft speed difference is picked up by the atb. So it does not act like a open diff with all 4 wheels on the ground and when one wheel slipps/spins through loss of traction causing the 2 prop shafts to spin at different speeds. The atb splits the torque and automatically the vehcile feels more stable and planted. I did a write up some where on here when i got it. Ps if you don't then you are not entitled to pass comment as you don't have first hand experience of a atb diff centre in your centre diff of your defender, this is a factual statement and only experienced people with first hand experience should comment [emoji8](thats in response to your "pro driving " comment about me)

[tact]

[...]Ps if you don't then you are not entitled to pass comment as you don't have first hand experience of a atb diff centre in your centre diff of your defender, this is a factual statement and only experienced people with first hand experience should comment [emoji8](thats in response to your "pro driving " comment about me)

Fair enough.

[1nando]

One more video. Now this showcases the difference with the cdl locked and unlocked in slower situations. Please note how the vehicle drives with a open cdl and all wheels on the ground. Power is sent to one wheel only on which ever axle has the least resistance. Please note how leaving the cdl unlocked never allows for 2 wheels (1 at the front and 1 at the rear) to spin at the same time, only 1 will ever spin at a time as this is npt true 4wd. The path of least resistance will only ever travel to one wheel when unlocked so how people are reporting one front and one rear wheel spinning at the same time is beyond me without either a torsen/atb or a viscous coupling diff centre.
True 4wd will always provide drive to one front and one rear wheel at a even split of torque, with the cdl unlocked a defender is not in true 4wd but rather a 1 wheel drive.

Please read the info in the description also. CDL should always be engaged when off the tarmac.

Enjoy
YouTube (https://youtu.be/6FgvD7D8Nl8)

[Summiitt]

This is an interesting thread, with a breadth of ideas and opinions. Here’s how we do it, I’ve got 6 Defender tray tops running in Forestry and fire management, loaded all the time, most of my guys have never had experience with the Defender full time system before working for me. Basically we never lock the diff on fast dirt or tracks where there is no weight being lifted off axles. As soon as there is weight transfer off the front axle, ie, steep inclines, I insist the diff is locked, as well as any low range situations. Obviously if the forestry roads turn to slush and there’s a risk of sliding or loosing control we will lock the diff in. I see no need at all to lock the centre diff on dirt roads where your road speed could be up to 80km/h.. maybe this comes down to experience driving on these roads. I’ve never had a transfer case, or centre diff failure and 4 of these utes have +400,000km on them.
At the end of the day, this is what works for us and I don’t believe in forcing my ideas down the throat of others, do what your comfortable with and what works for you.

[AK83]

One more video. Now this showcases the difference with the cdl locked and unlocked in slower situations. Please note how the vehicle drives with a open cdl and all wheels on the ground. Power is sent to one wheel only on which ever axle has the least resistance. Please note how leaving the cdl unlocked never allows for 2 wheels (1 at the front and 1 at the rear) to spin at the same time, only 1 will ever spin at a time as this is npt true 4wd. The path of least resistance will only ever travel to one wheel when unlocked so how people are reporting one front and one rear wheel spinning at the same time is beyond me without either a torsen/atb or a viscous coupling diff centre.
True 4wd will always provide drive to one front and one rear wheel at a even split of torque, with the cdl unlocked a defender is not in true 4wd but rather a 1 wheel drive.

Please read the info in the description also. CDL should always be engaged when off the tarmac.

Enjoy
YouTube (https://youtu.be/6FgvD7D8Nl8)

Nando!
I think you just have to accept that no matter what it is that you have experienced, someone else will have experienced something else!
No amount of videos will help you learn that. Only experience will.

You said that power will be sent to the wheel with least resistance. What if that 'least resistance is equal on more than one wheel?
Where does the power go in that situation? Only to 'one wheel'?

When you say this:

"note how leaving the cdl unlocked never allows for 2 wheels (1 at the front and 1 at the rear) to spin at the same time, only 1 will ever spin at a time as this is npt true 4wd."

What happens when two wheels have the same amount of resistance? where does the power go then .. only to one wheel?
Think about it for a minute!
On a bitumen road in ideal conditions .. which wheel(s) have more, less or the same 'resistance' .. and where does the power go?
Leaving the CDL unlocked in the bitumen road situation, does the car drive only via one wheel, or two, or three, or four wheels?

I think you just have to accept that there exists a number of different situations than you have yet experience in your life.

[ozscott]

It's what makes AWD Land Rovers so great compared to part time 4wd in both dry bitumen and wet bitumen alike (ie open centre). Even decelerating mid corner the vehicle is gripping better from being an all paw versus rear only.

Cheers

[trout1105]

If people choose not to engage the CDL then that is entirely up to them after all it is their Landrover and they can use it as they wish.
However there is some pretty compelling evidence that if in certain situations the CDL is not engaged it can be damaged or you will find it more difficult to proceed with it unlocked.
Like I sad it is YOUR Landrover But where is the harm in trying using the CDL engaged when off the blacktop to see for yourself if it makes any difference in the way your truck handles or engaging it Before you hit the beach to see if you can finally go past that spot you always seem to end up bogged at.
It costs absolutely nothing and practically no effort to try this, Besides if the CDL isn't needed then why did LR reinstate them in the D2a's and many people with D2's retro fit them?

[bee utey]

What is worse for your transfer case, forgetting to engage CDL in high range for a section of perfectly good dirt road, or forgetting to disengage it when you hit the bitumen again? Both are equally plausible considering that most people don't concentrate 100% on every slight change in conditions.

Oh and as for beach sand, of course that's when you engage CDL, that's a no brainer.

[Zeros]

So far we’ve only heard of the potential for damage to the transfer case with the CDL unlocked. ...It would be very interesting to hear if anyone has actually suffered transmission wind up, to the extent of damaging the vehicle, as a result of the CDL being locked for too long, on the wrong surface, at the wrong time? Has this happened to anyone?

[PhilipA]

IMHO damage from windup often shows itself at a later date.

Who can say if those people who have Double Cardans fail have not had extreme wind up prior.
But the common sense answer would be that this would be a very likely outcome.

I know of diffs that have failed on the way home after hard offroad trips.

Personally I once had a FJ40 that I had to reverse for hundreds of metres to be able to shift out of 4WD, and then I broke the knob off the stick doing it. And that was on Fraser island on the old mining road which had many potholes and sand patches.
Regards Philip A