Quick Centre Diff Lock question..

[Sue]

Well I hope it's quick lol..

I am just curious as to what is the fastest you can drive when using the centre diff lock..? for instance if I felt that I wanted to use it when driving on a slippery gravel road at 80kms hour etc..

Just asking as I have been given conflicting advice on this and am more curious than anything else.. :)

[isuzutoo-eh]

As fast as you dare on a gravel road, as long as there is traction to be lost it will be okay.

[Symo]

I think its 60K provided your front wheels are straight ahead..... Does it not have a little sticker bizzo in front of the gear knob.... next to the sticker that shows the shift pattern?

[Disco Muppet]

Why are you driving on a slippery gravel road at 80kms? :p
AFAIK it's not really an issue how fast you drive, but it becomes an issue if you drive with it on sealed roads with corners and stuff, as it puts strain on various components.
That said, I don't drive particularly quickly when I have my CDL engaged.
All from my very limited technical understanding :)
Cheers
Muppet

[EchiDna]

it aint how fast you go, its how quickly you stop ;-)

[debruiser]

Doesn't the sticker mean you can engage the lock at 60km/hr. I dont see that there would be a problem with driving as fast as you like/are game. Personally I used to drive my 2wd ute at 80+km/hr on dirt/gravel roads with no problems. I do drive my series 3 as fast on gravel as I do on bitumen... sometimes I go faster on the dirt.....

[Yorkie]

As fast as you dare on a gravel road, as long as there is traction to be lost it will be okay.

Agree, so long as your wheels can slip/spin by losing traction you can remain locked, once on firm surface disconnect.
Sue, Have you read your manual or did you have a 'boys' look. ;):p

[Naks]

As fast as you dare on a gravel road, as long as there is traction to be lost it will be okay.

As a rule I do not exceed 80kmh on gravel roads. I've driven all day for days on gravel with CDL locked with no issues.

[MR LR]

As fast as a Defender will go is fine :p

[Loubrey]

Hi Sue,

Engaging the CDL on any gravel road is taught as good practice. It adds stability to the car and reduces the tendency for over steer (loose tail end).

As the guys mentioned before, a Defender can go as fast as it is safe to drive in CDL High.

The 80km/h limit Naks mentioned is also taught as good practice...

Cheers,

Lou

[debruiser]

Sorry Sue I'm going to ambush your thread....

Is traction control active with the diff unlocked? OR does it just activate when the diff is locked?

Obviously I realise that the traction control will not be able to give the same results as a locked diff, but shouldn't it activate during gravel/dirt road driving and help improve drivability?

[Sue]

Thanks everyone! I do admit to taking a 'boys look' to find the answer :p But your answers have cleared it up for me.. :)

and I think Debruiser that traction control is present even when the diff is unlocked.. (if I am wrong someone should be along shortly to correct me on this).. :)

[BigJon]

I am just curious as to what is the fastest you can drive when using the centre diff lock..?

As fast as you want to. It is a difflock, not a speed limiting device.

[chook73]

Sorry Sue I'm going to ambush your thread....

Is traction control active with the diff unlocked? OR does it just activate when the diff is locked?

Obviously I realise that the traction control will not be able to give the same results as a locked diff, but shouldn't it activate during gravel/dirt road driving and help improve drivability?

Traction control is always active but I have never had it activate at speed I am not sure if there is a maximum speed for it to work. Traction control works by applying the brake to the wheel which has lost traction which I would expect is not ideal at 80km/h on gravel.

Sent from my iPhone using Forum Runner

[camel_landy]

As fast as you dare...

...just don't use it on sealed roads.

M

[Westie]

We did some testing on the dirt roads around Alice Springs that demonstrated that in a (older leaf spring all round) Toyota Troop Carrier braking distances were significantly shortened if you were driving in 4wd. I can't remember the actual distances, but I do remember it was an emergency stop from 100km/h. In the Defender having the centre diff locked did not make any difference to braking distances which were comparable to the Toyota with 4wd engaged.

Apart from that - drive as fast as conditions & experience allow, and having the diff engaged does seem to make the back end less twitchy on loose gravel. This will especially be the case with a short wheel base.

[Sue]

We did some testing on the dirt roads around Alice Springs that demonstrated that in a (older leaf spring all round) Toyota Troop Carrier braking distances were significantly shortened if you were driving in 4wd. I can't remember the actual distances, but I do remember it was an emergency stop from 100km/h. In the Defender having the centre diff locked did not make any difference to braking distances which were comparable to the Toyota with 4wd engaged.

Apart from that - drive as fast as conditions & experience allow, and having the diff engaged does seem to make the back end less twitchy on loose gravel. This will especially be the case with a short wheel base.

Excellent.... I feel a lot better about it now!

Thanks.. :)

[Hymie]

We did some testing on the dirt roads around Alice Springs that demonstrated that in a (older leaf spring all round) Toyota Troop Carrier braking distances were significantly shortened if you were driving in 4wd. I can't remember the actual distances, but I do remember it was an emergency stop from 100km/h. In the Defender having the centre diff locked did not make any difference to braking distances which were comparable to the Toyota with 4wd engaged.

Apart from that - drive as fast as conditions & experience allow, and having the diff engaged does seem to make the back end less twitchy on loose gravel. This will especially be the case with a short wheel base.

Well it wouldn't would it.
An AWD with it's Center Diff Locked is the same driveline configuration as a Part Time 4WD with hubs Locked and 4WD selected through the transfer case.

[Westie]

Well it wouldn't would it.
An AWD with it's Center Diff Locked is the same driveline configuration as a Part Time 4WD with hubs Locked and 4WD selected through the transfer case.

I probably wasn't clear enough.

One of the points I was trying to make that was (kind of) related to the post was that engaging the centre diff lock in the Land Rover didn't make a significant difference to braking distance. I was surprised by this as I assumed that braking distance when not having the centre diff locked would be somewhere between the Toyota's 2wd and 4wd braking distance for the reasons you suggest.

[schuy1]

Traction control does not activate at speeds over 80KMH I think. Seem to have read that somewhere, in specs maybe
Cheers Scott

[rick130]

As for what speed you can be travelling when the CDL is engage, it doesn't matter, there will be no limit, all you really need is that the front and rear axles are travelling at the same speeds.

I've been known to slip it in and out at 100km/h :angel:

As for gravel road speeds, it all depends on the road surface, tyre type, tyre pressures, your skillset, run off, etc, etc.

The old 'drive to the conditions' comes to mind and use your common sense.

[disco2_dan]

Well I've been wondering about cdl on my d2 myself, I've engaged on the move lots now, any where from 2kph to 60kph but was wondering if I'm ment to be engaging on the fly? As I've never heard a crunch grind or even had any trouble engeging it I'm starting to think that it's ok to do? Also with TC I've had engage at around 80kph I was on a dirt road near the farm (hargraves) and hit some corrigations that made the car skip a little ( was around a corner that dropped away aswell!!) and traction control flashed on but it didn't seem to noticeable what ever it did, so I'm not 100% I was doing over 80kph but I know I was doing 90kph when I first hit the corrigations but soon as I felt the car start to skip/slide a little I was to focused on the road/car to look at the speed and i didn't look down until after and the speedo said 75ish and the TC light was still on for another 2 or so seconds

[rick130]

As long as you are travelling in a straight line and the wheels aren't spinning you can engage/disengage the CDL
(and if you can spin your wheels at 100km/h plus, can I have a drive, please ? :D)

[Westie]

Well I've been wondering about cdl on my d2 myself, I've engaged on the move lots now, any where from 2kph to 60kph but was wondering if I'm ment to be engaging on the fly?...

As rick130 says, it doesn't matter what speed you're going. What matters more is to engage the centre diff before you loose traction - you don't really want the front & rear wheels rotating at wildly different speeds when you lock the diff.

So - bottom line - if you're on a loose(ish) surface and you're not sure, better to lock the diff than not.

[Jode]

Sorry, but I can't get my head around the idea that braking distance at a given speed will be shorter for a 4wd vehicle when 4wd is engaged. If each wheel has a brake, then applying those brakes will reduce the wheels' tendency to turn and by so doing reduce the vehicle's speed. How will the fact that all 4 wheels are under drive (or when in 2wd, only 2 wheels) affect brake performance?

[Tikka7mm08]

I thought the same when I read that...but then I was thinking silicon hoses must be some sort of performance upgrade too so hopefully someone can clear this one up!

[Ancient Mariner]

All to do with weight transfer the rear wheels can lockup and skid not good:(
With the center diff locked the rears maintain the same speed as front as long as you have a rear locked diff[ not the best;) ditch the front tailshaft lock the center diff and drive it like you stole it:angel: not recomended but fun just the same:D

[Jode]

Brake lock is caused by a lack of traction - if the tyre looses grip when braking then the brakes stop the tyre from spinning, hence the lock - if I understand correctly. So then, a tyre under drive will have more traction than a tyre carrying vehicle weight only (the 2 undriven tyres of a 4x2), so the risk of brake lock on a 4x4 would be less than on a 4x2. That makes sense - thanks for the clarification!

[Sitec]

Interesting one this! Ok, first, the CDL... As everyone before has said, no problem engaging it when on the move on dirt when in a straight line. Just don't do it when going around corners or when you are stuck with the wheels spinning!! If you are traveling in a straight line, both axles are covering the same distance.... so the center (transfer box differential is rotating as one lump and the bevel gears within this diff are stationary). If you are turning in a circle, the front axle is traveling in a greater arc than the rear... This means that it it is going marginally faster than the rear axle... (The longer the wheelbase, the greater the speed difference between the two axles). At this point, the small bevel gears in the center differential are rotating within the housing (which is also rotating!). All very confusing, but this means that the two interlocking halves of the center diff lock are rotating at different speeds so must not be engaged... Hope that made sense and helped a bit!!

Re braking hard, yes you are right in thinking that all the wheels should be braking the same amount, BUT, they never really do.... As said before, when you stand on the anchor pedal, you get thrown forward and upward.. You can't see it, but so does the rear of your Land Rover.. (unless you are driving a series vehicle!!:D) Stand on the brake pedal hard enough, and there can be very little weight on the rear wheels... meaning they lock (becoming fairly ineffective..). This is made worse on dirt because the left wheel is usually on the looser gravel, so is also loosing traction.... if it does, and your rear wheels are locked, suddenly the only wheel with any grip and being of much use is the front right. When this happens, your rear end suddenly decides to overtake your front end in a clock wise direction!! All great fun if you are expecting it, but not so much if you are in a 130 with an overloaded roof in a foreign country. (Just ask my SWIMBO)!! Sooooooo, by having the center differential LOCKED, when you do plant your foot on the STOP pedal, you are lessening the chance of the rear wheels locking as they are directly locked/linked to the fronts, and if you do manage to press hard enough and get all four wheels locked, at least you are still traveling in a reasonably straight line!! Also, with the center diff locked, you WILL have to stall the engine to lock all four wheels, whereas with it unlocked, if you lock the rears and manage not to stall the engine, it will try and drive the fronts and keep going!

Turned out a bit longer than planned but hope it makes sense and helps!!!! :)