Halfshaft clutches - please can someone explain

[Panda]

I was reading an article about an Ibex 4WD trophy comp, where they apparently spectacularly rolled down a hill ...

" ... 4F 022 was lined up to go first and a brief team confab resulted in the decision to go down with both lockers (http://www.ebroadcast.com.au/ecars/A/Diff.locks.html) engaged. Frankly we needed maximum engine braking, regardless of the effect this configuration would have on the steering. Suddenly there was an air of tension in the lead Ibex, and Juha very carefully strapped himself into the full harness for the first time that weekend. I reached for the grab-handle and offered my navigator's final words of wisdom: "Just keep it straight Patrick". Within five yards it had all gone totally pear-shaped.

The Ibex had full body weight on its front legs but unfortunately one of them was broken. There now followed a pronounced lurch, the steering was ripped violently from Patrick's hands and the vehicle staggered drunkenly to the left, climbing the bank in suicidal fashion. What happened next is lost in a blur of tumbling light patterns and a cacophony of sound. The windscreen shattered into a dull mosaic and something whistled through the tiny gap at the top of the mesh bulkhead and joined us in the front. This something later turned out to be the old viscous fan unit.

We stopped rather quicker than I expected, seemingly totally inverted and with nothing but bare earth visible through the remains of the windscreen. Eyewitnesses say the Ibex tried to climb a tree before going into a spectacular full-twisting somersault. All I can say is that our final resting-place was very precarious indeed and we could do no more than hang helplessly upside-down in the harnesses awaiting rescue ...

... Our rollover was caused solely by attempting to drive-on with all ARB diff-locks engaged for 3WD. The vehicle went AWOL so quickly and in such spectacular style that it really scared everybody into some preventative action. The principal "event-Ibex" all now have halfshaft clutches fitted to the front halfshafts ... expensive at about £300 a pair but you never again break another front halfshaft ..."

:confused::confused:

[Blknight.aus]

the way Im reading it is that its a torque limiting device so that in the event of massive overload it just slips. Sort of like a clutch but different.

theres a few versions of it most a varient in one way or another of a sprag (like the one that mounts the stator in a TC) clutch or a viscus friction pack (like the one in a viscus fan or the viscus slip limiter in a rangie).

Not sure Id want them in the halfshaft assembley as most basic versions only have a limited number of "slips" before they start to deteriorate. they then either become free wheeling (like the sprag in an overworked TC) or lock solid( like the ones in the rangie slip limiter)

I can understand why they want them, in theory, it would give you the ultimately reliable halfsaft.

[Panda]

Thanks Dave, my next question ... how common would it be for a broken half shaft in conjunction with a front locker, to cause that sort of dramatic "mishap", for want of a better word? Would it be a one off type of event, or more common. And why would it lose control to such an extent if it had a rear locker engaged, unless the rear wheels were off the ground at the time?

(Not that I'm paranoid you understand!:eek:)

[abaddonxi]

Something like Ashcroft's Cush Drive?

Ashcroft Transmissions (http://www.ashcroft-transmissions.co.uk/part_59.html#pa2)

Think someone mentioned them a week or so ago.

Cheers
Simon

[Blknight.aus]

no, not like that. they provide a dampning, and reduce shock loading which is a very good thing but at the end of the day they will still provide a positive drive so if you lock a wheel solid and then jam 40000000000000000 nm of torque onto it it will still snap something.

the clutch would provide a release at X nm of torque and just keep spinning and generally make a lot of heat in the mean time.

Those crush drives are what I would be fitting if it was me.


the reason why it would have speared off will be at least 3 fold

1. Driver error, he should have ridden the brakes and left the front diff open. A standard procedure for going down hill under engine braking, you need to be able to steer and the locked rear will keep the back going slower than the front (till all traction is lost on the rear anyway)
2. Driver error, if he knew he had the problem and took no other precautions to prevent the vehicle from running away from him and loosing control, if he didnt know because hed been driving around all day locked up at what point did he ever do a check and, if he had just gotten into the vehicle why didnt he test everythings functionality first?
3. Driver error with a broken vehicle he was going to attempt an obstacle, if hed asked himself the 3 golden questions he should have gotten a no at question 2 or 3. (negating that question 1 is generally irrelevent in a comp)
4. the vehicle would have lost traction at some point on the rear axle (it would have been trying to overtake the front and get down the hill first) and the only retardation to this would have been the single front wheel with engine braking applied this would have turned the vehicle cross slope and caused it to roll.
5. being in a comp odds are it had an auto (or if a manual he may have been riding the clutch) , he may have not gotten the TC fluid coupled correctly prior to descending(or fully released the clutch and then when it hooked up it would have caused a sudden unexpected retardation which would have a, slid the vehicle to the side with the least braking effort b, yanked the steering wheel around uncontrolabley all of which would have made the vehicle try to cross slope at a fair clip.

[isuzurover]

I assume they mean GKN overload clutches or similar...


To help preserve the shafts and to avoid time consuming front shaft replacement the front axle has GKN Driveline Overload protection hubs. These work through a set of pre-torqued discs that allow slippage when high sheer loads begin but pull back the drive when the stress has dissipated. There were developed for use by the Army with their Wolf Defenders in front line action.

[Reads90]

I assume they mean GKN overload clutches or similar...


Yeah they are talking about GKN overload Hubs.

I had them on my winch challenge 90

They we designed a a sort of cental fugal clutch . So when the wheels spun in the air when they came down (which is the quickest way to break a half shaft ) they disengaged the front shafts and rengaged when the load was safe to
Look at the pics and you can see them on the front hubs

https://www.aulro.com/afvb/images/imported/2009/04/120.jpg

https://www.aulro.com/afvb/images/imported/2009/04/755.jpg

This is the set up i had on the front of my 90 , Standard shafts and Arb locker with Kam 4.7 ring and pinion . I could use standard shafts as i had the GKN overload hubs as you can see here on the left

https://www.aulro.com/afvb/images/imported/2009/04/756.jpg

Me and my brother both had them on our winch challenge 90's . I remeber Marcel ( from here) came to see me and my brother when i was in the uk and we went off roading . where my brotehr showed him what they could do . He put both front and rear lockers in on his 4.2 V8 90 and the put it on full lock and floored hit and did loads of donuts around and around . Much to Marcels surprise

[Blknight.aus]

yes more like them (Id imagine)....

and sorry panda...

that kind of mishap would be more frequent than you'd think under those conditions.

[Panda]

Thanks Dave ... dont' think that's what I wanted to hear though ... :eek::D

Might have to do a bit more investigating ... mind you, the SIII has had a front locker for well over 10 years, & (touch wood), never had any problems with anything breaking. Maybe I'm just lucky!


yes more like them (Id imagine)....

and sorry panda...

that kind of mishap would be more frequent than you'd think under those conditions.

[Reads90]

Thanks Dave, my next question ... how common would it be for a broken half shaft in conjunction with a front locker, to cause that sort of dramatic "mishap", for want of a better word? Would it be a one off type of event, or more common. And why would it lose control to such an extent if it had a rear locker engaged, unless the rear wheels were off the ground at the time?

(Not that I'm paranoid you understand!:eek:)

This is what happen to my brother when his front half shaft broke with both front and rear locker in and 4.2 V8 :o

YouTube - 90 rolls

[isuzurover]

Thanks Dave ... dont' think that's what I wanted to hear though ... :eek::D

Might have to do a bit more investigating ... mind you, the SIII has had a front locker for well over 10 years, & (touch wood), never had any problems with anything breaking. Maybe I'm just lucky!

It is quite simple to avoid. Only ever engage the rear locker when going downhill...

Reeds90 - can't see how the broken axle had much contrribution to flipping when driving UPhill - but I suppose on slippery mud with too much right foot anything is possible.

I have seen plenty of comp vehicles drive all sorts of terrain with a broken CV - still using the front locker. Unless you are driving down very muddy hills, I can't see this being a big issue.

Another thing to remember is - if you lose traction or start going sideways when driving downhill, ACCELERATE. Most people panic and hit the brakes, when they should be stabbing the accelerator to gain traction and straighten the car up.

[Reads90]

It is quite simple to avoid. Only ever engage the rear locker when going downhill...

Reeds90 - can't see how the broken axle had much contrribution to flipping when driving UPhill - but I suppose on slippery mud with too much right foot anything is possible.

I have seen plenty of comp vehicles drive all sorts of terrain with a broken CV - still using the front locker. Unless you are driving down very muddy hills, I can't see this being a big issue.

Another thing to remember is - if you lose traction or start going sideways when driving downhill, ACCELERATE. Most people panic and hit the brakes, when they should be stabbing the accelerator to gain traction and straighten the car up.

mmm more was the fact it was a viscous Auto box that with the combination of the lockers and the broken shaft , caused power to be shifted to the rear wheels causeing this problem . So what happen he was going up a very steep hill . More than 45 degrees and just about at the top when the shaft broke and the auto box sent the power to the back axel and too much power .. It was the 6th time he had gone up the hill . The other 5 times no problem

[Blknight.aus]

its not something to worry about...

they screwed the pooch... from right here....


resulted in the decision to go down with both lockers engaged. Frankly we needed maximum engine braking, regardless of the effect this configuration would have on the steering

and then this little pearler

I reached for the grab-handle and offered my navigator's final words of wisdom: "Just keep it straight Patrick"

would be totally contradictory.

hows he ment to steer it if the front wheels are locked together drive wise so cant negotiate a turn?

if hed checked his drive line (easy in a series, drop out the diff lock put it in 2wd and hand turn the front propshaft then try to drive it forwards a little if it wont drive forwards youve done a rear shaft, if you can turn the prop youve done a front) he would have realised what his immediate problem was going to be...

IF he'd used his brain he would have set up differently...

IF you have the front wheels locked to the rear wheels (all 3 difflocks in) as soon as you get any skipping on the rear you're nearly screwed as is with a broken front half shaft if you skip towards the broken shaft youve had it and in most cases your going to be flat bedding the vehicle back and if your lucky you'll be in the ambulance but wont be zipped into one of the body bags they carry.

Heres why.

with all 4 wheels locked together if the rear starts to overtake the front there is nothing you can do to sort it out you cant make an effective turn (untill you lift of spin a front wheel) and you cant just lift off of the brakes as the front axle is only ever going to spin at the same speed as the rear axle.

with the cdl and the rear on the engine will always retard the back wheels equally so if the rear tries to over take the front you just take your foot off of the brakes and the drag of the rear end against the engine or handbrake (LR's and other propshaft braked vehicles only) is more effective against the rears so the vehicle will try to straighten up going down hill, this is even more apparent if you unlock the Center diff as well. Added to this is the fact that with the rear wheels locked together they naturally will add a breaking effort if one wheel needs to turn faster than the other (try pushing a cone shaped basket in a straight line you'll soon work out what I mean)

assuming you know how a bobcat or dozer steers happens when we couple one front wheel to both back wheels. its going to turn and heres where it gets worse... IF your'e trying to engine brake when that happens its also going to yank the steering in that direction. This is going to make the situation worse and its going to kick the tail end of the vehicle out....

and thats all she wrote. From this point on your pretty much just a passenger on a roller coaster ride in a lesson of physics no matter which side of the vehicle your on or what controls are in front of you.

[leeds]

It is quite simple to avoid. Only ever engage the rear locker when going downhill...




Can you please explain this comment.

Only have a rear ARB locker in the 110 and engage it when think going to have difficulties in going uphill or am likely to get bogged in the mud.

Always looking to understand more.

Regards


Brendan

[isuzurover]

Can you please explain this comment.

Only have a rear ARB locker in the 110 and engage it when think going to have difficulties in going uphill or am likely to get bogged in the mud.

Always looking to understand more.

Regards


Brendan

Just so my comment is clear - if you have F&R lockers fitted, when going downhill it is best to engage the rear only if you are worried about the scenario mentioned above.

If you are driving down a steep, rutted hill (or one with slippery and grippy patches for that matter):
In a vehicle with open diffs at both ends, you will often lurch forward at times when one wheel at each end comes off the ground (or has low enough ground pressure etc to lose traction)
In a vehicle with a rear locker engaged, you descend smoothly, as long as at least one rear has traction at all times. The rear locker engaged also helps keep the car straight.
With F+R lockers engaged, you have some extra control, except you have little or no steering, and it does not assist with keeping the car going in a straight line like the rear does.

I engage my rear locker whenever I am going down a hill that is steep (or rutted/rocky/loose/muddy) enough. It makes a HUGE difference.

[Panda]

Thanks ... that's sooooooooo reassuring ... :eek::eek::D


This is what happen to my brother when his front half shaft broke with both front and rear locker in and 4.2 V8 :o

YouTube - 90 rolls (http://www.youtube.com/watch?v=AOQDO2l2UNs)

[Panda]

Back up a bit Dave (I'm easily confused! :D)






hows he ment to steer it if the front wheels are locked together drive wise so cant negotiate a turn? :confused::confused: What do you mean "can't negotiate a turn?"


IF you have the front wheels locked to the rear wheels (all 3 difflocks in) huh???

with all 4 wheels locked together double "huh"

Screw it ... think I'll go back to knitting! :D:D

What do they say, "Ignorance is bliss". I can feel a very blissful moment coming on! :D:D

[isuzurover]

Back up a bit Dave (I'm easily confused! :D)

Never tried to turn a corner with your front locker engaged???

[Slunnie]

Never tried to turn a corner with your front locker engaged???
Thats something that a lot of people comment on, but when I do it.... well, the Disco just turns. The turning radius is increased a little, but nothing worth talking much about.

[isuzurover]

Thats something that a lot of people comment on, but when I do it.... well, the Disco just turns. The turning radius is increased a little, but nothing worth talking much about.

Ever tried it in a series landie with Armstrong power steering??? ;):D

[Panda]

Yes, all the time. The locker is engaged as soon as you put it in low or 4WD.


Never tried to turn a corner with your front locker engaged???

[isuzurover]

Yes, all the time. The locker is engaged as soon as you put it in low or 4WD.

Now you have me confused... Which vehicle are you talking about and what front diff lock is fitted?

[Panda]

God you're up late!!! You're confused ... not half as confused as I am! :D:D:D

I'm talking about my Series III. Detroit. (Now do you see why I'm a bit concerned???) :)


Now you have me confused... Which vehicle are you talking about and what front diff lock is fitted?

[isuzurover]

God you're up late!!! You're confused ... not half as confused as I am! :D:D:D

I'm talking about my Series III. Detroit. (Now do you see why I'm a bit concerned???) :)

Ahh - all is clear...

EDIT - scratch this bit - see below...

If you snap an axle, the detroit is known to grenade, so you need not worry :D:eek::p
e.g. - see here: broke an axle and my Detroit quit working 2 days later - NAXJA Forums -::- North American XJ Association

2hrs later where you are !

[Panda]

Ahhhhhhhhh, thanks! That explains it. :D:D What does "grenade" mean???

In that case, you're up extremely late :eek::eek: And your brain's still functioning! :D:D


Ahh - all is clear...

An auto locker like the detroit is UNLOCKED until you need it. So when you engage 4x4 (or low range), the detroit is still unlocked. Only when 1 wheel starts to turn faster than its opposite number will the detroit lock.

If you snap an axle, the detroit is known to grenade, so you need not worry :D:eek::p

2hrs later where you are !

[isuzurover]

Sorry - that was the other way around... (it IS too late...).

The detroit etc is LOCKED until you need to turn a corner. Then it unlocks.

Grenade = big kaboom.

[Panda]

:Rolling::Rolling:Yea, I know what a grenade is, I meant can you explain what actually happens technically ...




Sorry - that was the other way around... (it IS too late...).

The detroit etc is LOCKED until you need to turn a corner. Then it unlocks.

Grenade = big kaboom.

[isuzurover]

:Rolling::Rolling:Yea, I know what a grenade is, I meant can you explain what actually happens technically ...

AFAIK, the shock-loading when the axle breaks can strip some of the teeth from the locking mechanism.

http://www.spriteparts.com.au/user/cimage/Detroit-Locker-dismantled.jpg

[Panda]

Thanks Ben. So ... bottom line ... I don't have to worry? Does that mean I've started this thread for nothing?? :eek::eek::Rolling:

[isuzurover]

Thanks Ben. So ... bottom line ... I don't have to worry? Does that mean I've started this thread for nothing?? :eek::eek::Rolling:

detroit go bye bye...
http://pages.prodigy.net/dmacock/detroit/DSC02323.JPG

In 99.9% of offroad situations you will probably have no issues driving down a hill with a locked front or a locked front with 1 broken axle.

On the very rare chance you broke an axle just before starting down a steep muddy hill, then hopefully the detroit would break before anything happened ;). If not, there is a slight chance you could spear off the track, but chances are you could correct by steering or accelerating.

[leeds]

Thanks for your explaination Ben



Regards


Brendan

[Panda]

Thanks Ben! :D:D

[V8Ian]

How many and what type of lockers have you got Panda?

[Blknight.aus]

Back up a bit Dave (I'm easily confused! :D)

Not a problem panda, I'll do you a thread on diff actions tonight.

[Panda]

Hi Ian,

I've got a Detroit in the front & maxi's in the rear. :D


How many and what type of lockers have you got Panda?

[Panda]

Thanks Dave :)


Not a problem panda, I'll do you a thread on diff actions tonight.

[Blknight.aus]

is your front detroit a hard locker (air actuated like an ARB) or a soft locker like the true track that we were importing from the US (the one with the funny spiral cut gears inside)

if you have a hard locker at the back (like a maxi or ARB) and a soft locker up the front (the detroit true track) then dont worry what has happened here cant happen to you in the manner that it happened in the first story because of the way the true track works..... your best technical down hill setup would be to manually lock the CDL and the rear select an appropriate gear (1 or 2 low) and walk it down with your left foot up under the clutch pedal pulling it backwards towards the steering wheel, hands at 10+2 with your other foot on the floor near the accelerator.

A similar but different thing can happen and have you in the same boat BUT by the time you got yourself that wound up, cross axled and side sloped that more than likely you would have already been beyond the point of no return anyway and the diffs contribution would just be the straw after the straw that broke the camels back.

[Panda]

The Detroit is a trutrak from memory ... it's not air actuated. I can't recall what the gear look like, we put it in as an experiment well over 10 years ago now, & it's been in ever since - keep toying with the idea of removing it, but I must say that I like it, despite the fact that it makes the already heavy steering even heavier (epecially if you run low pressure tyres :eek::eek:)

The rear is a maxi locker ...

Can't say I've ever experienced any problems with either the front or rear locker. Don't worry about engaging the rear very often, as the front is usually enough.

Sorry didn't understand your "foot up under the clutch pedal etc ... " I just wack it in 1st (don't use 2nd much as it drops out - if it's particularly tricky it's too difficult to hold in 2nd & steer, though depends on the track), I don't worry about the clutch or brake ... just sit back & let the Landie do all the work. Obviously if going up a reaonable hill, have to use the accelerator. The steering's not that bad ... you get used to how to steer it with the front locker. Other people who have driven it seem to struggle with it, but I think they tend to fight against it & don't "feel" how to drive it. Tony's son drove it for the day not long ago, by the end of the day, he loved it & couldn't get him out of it :eek::eek: But he's a rarity! Most people don't like to drive it, especially going from a Rangie or Disco, as you have to work a bit & anticipate how to drive it. :D:D

But what can I say ... I'm a sucker for punishment! :D:D



is your front detroit a hard locker (air actuated like an ARB) or a soft locker like the true track that we were importing from the US (the one with the funny spiral cut gears inside)



if you have a hard locker at the back (like a maxi or ARB) and a soft locker up the front (the detroit true track) then dont worry what has happened here cant happen to you in the manner that it happened in the first story because of the way the true track works..... your best technical down hill setup would be to manually lock the CDL and the rear select an appropriate gear (1 or 2 low) and walk it down with your left foot up under the clutch pedal pulling it backwards towards the steering wheel, hands at 10+2 with your other foot on the floor near the accelerator.

A similar but different thing can happen and have you in the same boat BUT by the time you got yourself that wound up, cross axled and side sloped that more than likely you would have already been beyond the point of no return anyway and the diffs contribution would just be the straw after the straw that broke the camels back.

[isuzurover]

is your front detroit a hard locker (air actuated ...

An Air Actuated detroit??? You been into the EP90 again today Dave??? :D

AFAIK
There is the "old style" detroit locker (which I posted images of above) - an auto locker
There is the detroit EZ-locker or softlocker, basically a more refined (but weaker) version of the above.
Then there is a truetrac - which is NOT a locker, it is a geared Limited slip diff. EDIT - inserted this in the wrong spot: With a Truetrac, if you lift one wheel completely off the ground - or break an axle one assumes - the Truetrac will work like an open diff.
There is also the detroit e-locker and a few "lunchbox" lockers as well

Dave - instead of writing a tome on here on how diffs work (available everywhere if you google btw) - how about fitting that Provent... ;) :p



The Detroit is a trutrak from memory ...

If that is the case you have an LSD not a locker, and absolutely nothing to worry about.

My better half has been driving the IIA to work for the past few weeks. It has definitely raised her cred with the blokes at her work :D

[Panda]

It can't be a trutrac or whatever it's called then. I know it's not a limited slip diff.

Think I'll go back to my knitting now ... :eek::eek:



An Air Actuated detroit??? You been into the EP90 again today Dave??? :D

AFAIK
There is the "old style" detroit locker (which I posted images of above) - an auto locker
There is the detroit EZ-locker or softlocker, basically a more refined (but weaker) version of the above. IF you lift one wheel completely off the ground - or break an axle one assumes - the Truetrac will work like an open diff.
Then there is a truetrac - which is NOT a locker, it is a geared Limited slip diff.
There is also the detroit e-locker and a few "lunchbox" lockers as well

Dave - instead of writing a tome on here on how diffs work (available everywhere if you google btw) - how about fitting that Provent... ;) :p




If that is the case you have an LSD not a locker, and absolutely nothing to worry about.

My better half has been driving the IIA to work for the past few weeks. It has definitely raised her cred with the blokes at her work :D

[isuzurover]

It can't be a trutrac or whatever it's called then. I know it's not a limited slip diff.

Think I'll go back to my knitting now ... :eek::eek:

Come on Panda - just whip it out and snap a couple of pictures :o:wasntme:

[Panda]

:Rolling::Rolling:Dream on ... that ain't gonna happen! I have enough problems checking & changing all the oils!



Come on Panda - just whip it out and snap a couple of pictures :o:wasntme:

[Blknight.aus]

thats the problem with saying "theres a detroit in the front diff"

they make an open type diff, a traditional LSD, the one that works through the funkyness of compound planetry gearing, the ratcheted pawl locker and a couple of versions of a hard locker like an ARB...

its sort of like saying I have a holden ute... Yep its a holden, which one?

[Panda]

Yea, point taken Dave. I only know it's not a LSD because I remember when we were at a friend's 4WD workshop ... and the salesman came in & they were all discussing it for ages, about how it would affect the steering. And I decided, yea, I'll give it a go ... Plus the fact that when you're driving it in the bush, it does handle alot differently when you engage low or 4WD.


thats the problem with saying "theres a detroit in the front diff"

they make an open type diff, a traditional LSD, the one that works through the funkyness of compound planetry gearing, the ratcheted pawl locker and a couple of versions of a hard locker like an ARB...

its sort of like saying I have a holden ute... Yep its a holden, which one?

[Blknight.aus]

that causes me a bit of concern there panda....

If everything is set up for optimum life

(working on its done in a series)

the only change you should experience when you chuck it into 4wd is that occasionally when you work it hard over near lock the wheel fights you as the UJ's pass over center and do that thing they do that makes them UJ's and not CV joints.

(working on its anything newer than a stage 1)

nothing should change when you chuck it into low range or pull the CDL in

if your steering becomes funny as soon as you engage the cdl or four wheel drive then theres a few things that could be happening.

1. one or more cross axle diff lock has been setup to engage with the CDL or fourwheel drive. This has the potential to be bad.

2. you have an LSD in the front that has been set to tight, this is bad as it will not only cause potentially erratic behavior off road (as well as on) but it will cause premature wear in the front diff

3. you have an early detroit soft locker with the sprag clutches in the front. this can cause merry hell with your steering and the UJ's in the front axles of a series dont like the way it locks/unlocks much and theres a couple of very specific circumstances that can take out the axles/uj's if murphy decides to throw a bucket of hate your way.

[Panda]

And we were doing so well ... :eek::eek:

Knitting's looking good again! :eek::D:D


that causes me a bit of concern there panda....

If everything is set up for optimum life

(working on its done in a series)

the only change you should experience when you chuck it into 4wd is that occasionally when you work it hard over near lock the wheel fights you as the UJ's pass over center and do that thing they do that makes them UJ's and not CV joints.

(working on its anything newer than a stage 1)

nothing should change when you chuck it into low range or pull the CDL in

if your steering becomes funny as soon as you engage the cdl or four wheel drive then theres a few things that could be happening.

1. one or more cross axle diff lock has been setup to engage with the CDL or fourwheel drive. This has the potential to be bad.

2. you have an LSD in the front that has been set to tight, this is bad as it will not only cause potentially erratic behavior off road (as well as on) but it will cause premature wear in the front diff

3. you have an early detroit soft locker with the sprag clutches in the front. this can cause merry hell with your steering and the UJ's in the front axles of a series dont like the way it locks/unlocks much and theres a couple of very specific circumstances that can take out the axles/uj's if murphy decides to throw a bucket of hate your way.

[Panda]

Dave, I'm trying to remember when we got the Detroit ... I got the SIII in 1993 - I think it was a couple of years after that, so I'm thinking about '95 or '96. So possibly it's no. 3 - the older Detroit??

[Panda]

Just remembered - the swivels were leaking severely, so ended up taking it to Landie mechanic about this time last year. He found both axles were badly twisted ... which he reckoned was from the front locker. He suggested taking out the locker, or fitting free wheeling hubs. Any help??

[V8Ian]

Panda, are you saying that your front diff is permenantly locked? If so wouldn't that make FWH mandatory? It would also be hard on the entire front drive and tyres on all but the loosest of surfaces, whilst 4X4 was engaged.

[V8Ian]

:Rolling::Rolling:Dream on ... that ain't gonna happen! I have enough problems checking & changing all the oils!
I thought I was Robinson Crusoe ;)

[101 Ron]

I will chime in here.
Pandas description is normal for a detroit (unlocker) locker.
It is the same effect used in the cheaper versions Lockrite and Lockker which work on a similar principle.
Lockrite and lokker are common fitting in the front of Jap 4 bys due to the price and the true locked diff effect when needed off road.
The current detroit soft locker or series four locker is in a class off its own.
The other types of torque proportioning diff centres(true trac) and limited slip diff centres will not effect steering in 4WD in any way.( but dont 100% lock)
A auto locker will make the steering heavier on a part time system when fitted to the front.
The traction improvement is worth the heavier steering.
The heavier steering is not a result of the auto locker as it is more to do with it working with the rear diff in 4wd.
Remember a manual engaged locker is alot harder to steer again in 4wd and every thing locked in.
The GKN torque clutches on the front diff is a excellent way to save money and stop drive train damage.
In stead of forking out money for beefed up axles and diff centres, just use the torque clutches on the hubs as it will allow the drive train to become bullet proof on standard components.
The best use I can think of for this device is on farm tractor slashers.
It is fitted just in front of the slasher gearbox to protect it if the slasher hits a log or rock.............it just slips abit until the slasher blades can turn again under normal loads.
On a slasher they are simple , adjustable and reliable.
I wonder why they are not supplied as standard fitting on hard working 4 bys and why it takes the English army to get them fitted and developed.

[V8Ian]

Before I bought my car I test drove one with one of these type lockers in the rear. During brisk acceleration, while turning on a suburban intersection, I could feel the locker engage, causing the car to skip slightly sideways.

[Panda]

That's another reason I'm thinking it's a permanent locker ... you can't drive it on the bitumen, you'd probably end up killing yourself! It's really hard to steer ... :eek:


Before I bought my car I test drove one with one of these type lockers in the rear. During brisk acceleration, while turning on a suburban intersection, I could feel the locker engage, causing the car to skip slightly sideways.

[V8Ian]

Do you have free wheeling hubs Panda?

[Panda]

No I don't Ian ...


Do you have free wheeling hubs Panda?

[V8Ian]

That would mean that if your locker is permenantly engaged, even when in 4X2 the front wheels would have to rotate at the same speed. You must have the type that only locks when it detects slippage.

[101 Ron]

A detroit locker will only show any effects on the front diff of a part time system if it is connected to the rear diff...ie 4wd.
Free wheel hubs will not matter.
as I stated before it is the interaction between the locker and and rear diff which causes any steering heavyness.
Panda should remember my 101 going up a rocky step(the 101 has a stiff suspension and picks up wheels easy)and the rear detroit makes the difference when it counts.
you must remember the term detroit locker is very wrong,
It is a auto unlocker from full time locked, and unlocks for correct steering action.
A detroit inthe front of a series three would be of great help off road and now knowing that wish Panda took it to Yalwal that time.

[101 Ron]

Ps Panda
you do not strike me as the kniitting type !

[V8Ian]

Hey Panda, while you're weilding the knitting needles..........I've always fancied an aaron cardy with cable stitch on the front.......:p:tease::D

[V8Ian]

A detroit locker will only show any effects on the front diff of a part time system if it is connected to the rear diff...ie 4wd.
Free wheel hubs will not matter.
as I stated before it is the interaction between the locker and and rear diff which causes any steering heavyness.
Panda should remember my 101 going up a rocky step(the 101 has a stiff suspension and picks up wheels easy)and the rear detroit makes the difference when it counts.
you must remember the term detroit locker is very wrong,
It is a auto unlocker from full time locked, and unlocks for correct steering action.
A detroit inthe front of a series three would be of great help off road and now knowing that wish Panda took it to Yalwal that time.
I would personally prefer manually selectable lockers, ie. ARB.

[Panda]

How come it causes such grief on the bitumen then?


That would mean that if your locker is permenantly engaged, even when in 4X2 the front wheels would have to rotate at the same speed. You must have the type that only locks when it detects slippage.

[Panda]

Hi Ron, how's the 101 going? What an awesome vehicle ... was looking at some photos from that trip this morning.

Next time there's a trip to Yalwal will bring the Series III.

I still find this quite confusing ... all I know is:

(a) the steering becomes considerably heavier when in 4WD/low.
(b) if the maxi is engaged, there is no difference to the steering i.e. it does not appear any heavier.
(c) you cannot drive it on bituman if 4WD/low is engaged.

Thanks for your input Ron ... look forward to a trip! :D


A detroit locker will only show any effects on the front diff of a part time system if it is connected to the rear diff...ie 4wd.
Free wheel hubs will not matter.
as I stated before it is the interaction between the locker and and rear diff which causes any steering heavyness.
Panda should remember my 101 going up a rocky step(the 101 has a stiff suspension and picks up wheels easy)and the rear detroit makes the difference when it counts.
you must remember the term detroit locker is very wrong,
It is a auto unlocker from full time locked, and unlocks for correct steering action.
A detroit inthe front of a series three would be of great help off road and now knowing that wish Panda took it to Yalwal that time.

[Panda]

:Rolling::Rolling:Don't quite know how to take that Ron! :D:D Yes, am an avid knitter I'm afraid, amongst other things! Give me a pattern any time of the day to trying to decipher mechanics!


Ps Panda
you do not strike me as the kniitting type !

[Blknight.aus]

With your description I am almost certain you have an "unlocker" in the front. There is still scope for it to be a very badly setup limited slip diff but for this post we'll run with the assumption that its actually a detroit "unlocker" in which case.....

What Rons saying is close to the mark but isn't quite right.

What its doing has less to do with being hooked to the rear diff and more to do with it having a reaction force on the Crown wheel and pinion. Putting an "unlocker" in a front wheel drive car will produce a similar effect to what your getting but not to the same degree, I wont cover why its bad in a front wheel drive car in this post but will concentrate on why its bad in your particular setup.

If you know how it all works Rons got it more or less nailed and in short order we'll see if we cant help you out on that


what an "unlocker" is designed to do is lock both the axles together when you drive and when one wheel wants to turn faster it allows that to happen but it maintains positive drive to the wheel that is turning slower.

what that means is...

The inner wheel will rotate at the same RPM as the crown wheel and the outer wheel must speed up to compensate.

to explain what a detroit does I need to expand on the idea of the rolling cone I used earlier to explain why a diff was needed and what happens when you lock one up.

if you look at the cone as it turns its got 2 points of contact with the ground the inner (smallest circle) and the outer (largest circle) somewhere in the middle there will be another circle that moves at a pace thats halfway between the 2 outer circles. That middle circle will represent the Crown wheel of a diff in a car setup.

In a normal open diff when you drive the crown wheel turns at a rate that is half way between that of the wheels for example if you drive in a straight line with both wheels turning at 1 RPM then the diff turns at 1 RPM. when you go around a corner if the outside wheel turns at 1.5 rpm and the inside wheel turns at .5rpm then the crown wheel still turns at 1 RPM and you are in effect doing the same speed on the ground you're just turning a corner.

A Detroit "unlocker" makes things different.

It works by ensuring that positive drive is maintained to the wheel that is turning the slowest and it does this by utilising the normal innards of a Diff but with a pair of sprag clutches that mates each axle to the crown wheel. When you drive round a corner the inside wheels sprag clutch locks up, prevents slippage and drives that axle at exactly the same RPM as the crown wheel.

This is where it can get a bit mind bending.

what happens next is the outside wheel has to speed up, firstly because thats what happens when you drive round a corner secondly because the normal diff bits in the middle will drive it faster and the same sort of formula applies the diff needs to rotate at a speed in the middle of the 2 road wheels.

If you have the diff undriven (your landy is in 2hi) then the crown wheel simply matches pace and nothing untowards happens as there is nothing to restrict the crown wheel from doing whatever speed it wants. Its when you put a reaction force on the CWP that things get complicated.

in your series when you hit 4wd (4 hi/low) you are mechanically coupling the front diff to the rear diff there is no method for the 2 to turn at a different pace so what happens is this.

(Im going to simplify the maths on the next bit, the numbers I am going to use are not the numbers that would turn up in real life but will do to show the logic of whats going on)

you start to turn a corner and both crown wheels turn at the same speed, the rear diff being open (assuming you havent engaged the maxi) drives both rear wheels at an average speed of say 3 RPM so the inside wheel will be doing 2 RPM and the outside wheel 4 RPM at the same time the front diff will be doing its thing but the problem is that its thing is not the same as the rear diff.

the Detroit when its trying to drive the vehicle around the corner with the crown wheel turning at 3RPM will be driving the inside wheel at 3 RPM and the outside will want to be doing 5RPM.

given that all your wheels are the same size and that the following numbers are indicative of RPM not actual speed and your turning right lets put that along side each other


Front axle
L-D-R
5-3-3
4-3-2
L-D-R
Rear Axle

Notice how the front axle now wants to turn faster than the rear axle? Thats whats causing your problems, If you had a center diff like a county/deefer/rangie/disco the center diff would take up the difference (unless you lock it) but in a series as soon as you engage 4wd the crown wheels rotate at the same speed.

When you lock in your rear maxi the numbers look like

Front axle
L-D-R
5-3-3
3-3-3
L-D-R
Rear Axle

Which is better than the previous example but not by much.


Its been a very long while since I had to setup an old school detroit unlocker but from long vauge memory becuase they lock in the normal direction of drive and unlock on over run if you happened to be in the same cirucmstance as the Ibex in the initial post then the wheel with the unsnapped axle should be able to over run forwards and not retard the vehicles motion and steer it like a bobcat/dozer.

of course as mentioned in another post if you've hoiked an axle in a detroit "unlocker" then the diff lunches itself pretty smartly so you wouldnt be where the Ibex was in the first place because the drive line would either be locked solid OR youd have no front drive.



**********for the uber techy pick it apart guys****************
Yes, I know I over simplified the ackermans steering principals to get the numbers for the wheel speeds, deal.

[101 Ron]

I knew the detroit reacts with the rear diff , but didnt know why.
I just learn some thing.
Panda
The 101 is going well and the next time the landy troops decide to hit Yalwal I can put you guys up a the farm at kangaroo valley.
It is a good trip just to access the place.
Ron

[Panda]

Thanks for that Dave ... it's been a long night! :D

I understand perfectly now how the front diff works, the cone principle, etc ... have to go away & think about the connection with the rear diff now... :eek: :D:D

I wish I hadn't started this thread ... :Rolling::angel:


With your description I am almost certain you have an "unlocker" in the front. There is still scope for it to be a very badly setup limited slip diff but for this post we'll run with the assumption that its actually a detroit "unlocker" in which case.....

What Rons saying is close to the mark but isn't quite right.

What its doing has less to do with being hooked to the rear diff and more to do with it having a reaction force on the Crown wheel and pinion. Putting an "unlocker" in a front wheel drive car will produce a similar effect to what your getting but not to the same degree, I wont cover why its bad in a front wheel drive car in this post but will concentrate on why its bad in your particular setup.

If you know how it all works Rons got it more or less nailed and in short order we'll see if we cant help you out on that


what an "unlocker" is designed to do is lock both the axles together when you drive and when one wheel wants to turn faster it allows that to happen but it maintains positive drive to the wheel that is turning slower.

what that means is...

The inner wheel will rotate at the same RPM as the crown wheel and the outer wheel must speed up to compensate.

to explain what a detroit does I need to expand on the idea of the rolling cone I used earlier to explain why a diff was needed and what happens when you lock one up.

if you look at the cone as it turns its got 2 points of contact with the ground the inner (smallest circle) and the outer (largest circle) somewhere in the middle there will be another circle that moves at a pace thats halfway between the 2 outer circles. That middle circle will represent the Crown wheel of a diff in a car setup.

In a normal open diff when you drive the crown wheel turns at a rate that is half way between that of the wheels for example if you drive in a straight line with both wheels turning at 1 RPM then the diff turns at 1 RPM. when you go around a corner if the outside wheel turns at 1.5 rpm and the inside wheel turns at .5rpm then the crown wheel still turns at 1 RPM and you are in effect doing the same speed on the ground you're just turning a corner.

A Detroit "unlocker" makes things different.

It works by ensuring that positive drive is maintained to the wheel that is turning the slowest and it does this by utilising the normal innards of a Diff but with a pair of sprag clutches that mates each axle to the crown wheel. When you drive round a corner the inside wheels sprag clutch locks up, prevents slippage and drives that axle at exactly the same RPM as the crown wheel.

This is where it can get a bit mind bending.

what happens next is the outside wheel has to speed up, firstly because thats what happens when you drive round a corner secondly because the normal diff bits in the middle will drive it faster and the same sort of formula applies the diff needs to rotate at a speed in the middle of the 2 road wheels.

If you have the diff undriven (your landy is in 2hi) then the crown wheel simply matches pace and nothing untowards happens as there is nothing to restrict the crown wheel from doing whatever speed it wants. Its when you put a reaction force on the CWP that things get complicated.

in your series when you hit 4wd (4 hi/low) you are mechanically coupling the front diff to the rear diff there is no method for the 2 to turn at a different pace so what happens is this.

(Im going to simplify the maths on the next bit, the numbers I am going to use are not the numbers that would turn up in real life but will do to show the logic of whats going on)

you start to turn a corner and both crown wheels turn at the same speed, the rear diff being open (assuming you havent engaged the maxi) drives both rear wheels at an average speed of say 3 RPM so the inside wheel will be doing 2 RPM and the outside wheel 4 RPM at the same time the front diff will be doing its thing but the problem is that its thing is not the same as the rear diff.

the Detroit when its trying to drive the vehicle around the corner with the crown wheel turning at 3RPM will be driving the inside wheel at 3 RPM and the outside will want to be doing 5RPM.

given that all your wheels are the same size and that the following numbers are indicative of RPM not actual speed and your turning right lets put that along side each other


Front axle
L-D-R
5-3-3
4-3-2
L-D-R
Rear Axle

Notice how the front axle now wants to turn faster than the rear axle? Thats whats causing your problems, If you had a center diff like a county/deefer/rangie/disco the center diff would take up the difference (unless you lock it) but in a series as soon as you engage 4wd the crown wheels rotate at the same speed.

When you lock in your rear maxi the numbers look like

Front axle
L-D-R
5-3-3
3-3-3
L-D-R
Rear Axle

Which is better than the previous example but not by much.


Its been a very long while since I had to setup an old school detroit unlocker but from long vauge memory becuase they lock in the normal direction of drive and unlock on over run if you happened to be in the same cirucmstance as the Ibex in the initial post then the wheel with the unsnapped axle should be able to over run forwards and not retard the vehicles motion and steer it like a bobcat/dozer.

of course as mentioned in another post if you've hoiked an axle in a detroit "unlocker" then the diff lunches itself pretty smartly so you wouldnt be where the Ibex was in the first place because the drive line would either be locked solid OR youd have no front drive.



**********for the uber techy pick it apart guys****************
Yes, I know I over simplified the ackermans steering principals to get the numbers for the wheel speeds, deal.

[Panda]

It's all very mind boggling ... but getting clearer! :D:D

That sounds great Ron! As long as it's not too civilised ... :D:D




I knew the detroit reacts with the rear diff , but didnt know why.
I just learn some thing.
Panda
The 101 is going well and the next time the landy troops decide to hit Yalwal I can put you guys up a the farm at kangaroo valley.
It is a good trip just to access the place.
Ron

[V8Ian]

Maybe it's time to update, Panda. Go for a Disco and do it with style and comfort.:tease:

[Panda]

Well actually ... I'm quite partial to the Discos ... would love the new one that's coming out with the 4l V8! :D:D

However ... I'm actually thinking about a bike ... :wasntme:


Maybe it's time to update, Panda. Go for a Disco and do it with style and comfort.:tease:

[V8Ian]

Well actually ... I'm quite partial to the Discos ... would love the new one that's coming out with the 4l V8! :D:D

However ... I'm actually thinking about a bike ... :wasntme:
Motor :D or pedal :(;)

[Panda]

Motor ... bugger any unnecessary exercise! :D:D

Was going to start a thread ... on people's general opinions. Want something powerful, but as I'm so damn short, I have problems holding a lot of bikes up. Tony had a very nice BMW ex police bike, but I couldn't ride it, as it was too big!! :mad::mad: Was not amused! :D:D Was interested in a second hand Triumph Sprint quite a few year ago, but my feet wouldn't touch the ground! :D:D

Had a few bikes, the Kawasaki 650cc was really good, got a Yammy 750 I think ... it was a bit big, though okay once I was riding it! :D:D



Motor :D or pedal :(;)

[V8Ian]

Motor ... bugger any unnecessary exercise! :D:D

Was going to start a thread ... on people's general opinions. Want something powerful, but as I'm so damn short, I have problems holding a lot of bikes up. Tony had a very nice BMW ex police bike, but I couldn't ride it, as it was too big!! :mad::mad: Was not amused! :D:D Was interested in a second hand Triumph Sprint quite a few year ago, but my feet wouldn't touch the ground! :D:D

Had a few bikes, the Kawasaki 650cc was really good, got a Yammy 750 I think ... it was a bit big, thought okay once I was riding it! :D:D
VT 750 or 1100, nice low seat height and Honda bulletproofedness :D

[Panda]

mmmmmmmmmm ... 1100 ... mmmmmmmmmmmmm. Speed ... mmmmmmmmmmmmmm :D:D

Sorry, didn't mean to change the subject!


VT 750 or 1100, nice low seat height and Honda bulletproofedness :D

[Blknight.aus]

Ok so heres the interaction between the front diffs explained

Again keeping in mind that these are the super simple numbers to show the logic, in the example I gave you earlier you were making a right hand turn with the series locked in four wheel drive.

so your wheels and diffs were doing this.



Front axle
L-D-R
5-3-3

4-3-2
L-D-R
Rear Axle


the crown wheel (indicated by the letter D) rotates at a fixed velocity at both ends because at the end of the day both were driven by what is essentially the same shaft.

before we go on with the next bit go grab a normalish size vehicle (one with 4 wheels about the size of say a landrover 110/109) stick it on hard lock and drive in a slow circle on some sand, a wetish track or really clean cement, the objective is to leave tracks.

you'll notice you have 4 seperate tracks counting from the inside out they will be

the inside front wheel
the inside rear wheel
the outside front wheel
the outside rear wheel.

this is part of the ackerman steering principals and lots of funky geometry stuff for your car is worked out from that. as far as our problem is concered we just need some average wheels speeds so lets pretend that our wheels turn with these numbers for the same right hand turn that we made earlier

L---R
3---1
front
rear
4---2

now when we add in the diffs you get

L-d-R
3-2-1
front
rear
4-3-2

this highlights that the front diff is turning slower than the rear diff which is why your average series landrover has a plaque to the effect of

"use of 4wd on hard surfaces may redure tyre life"
or
"use of 4wd on hard surfaces may cause drive line damage"

because what that forces us to when you kick it into four wheel drive is

Front axle
L-D-R
4-3-2

4-3-2
L-D-R
Rear Axle

which in part is why the series steering wheel kicks when near lock and youve got it in four wheel drive. (that also ties into the effect of the Ujs when on a turn)

now because of how the detroit works coupling the crown wheel to the slowest wheel on the axle this means that the front axle now wants to travel faster than the rear (use the average speed of the wheels and ignore the diff speed)

as per

Front axle
L-D-R
5-3-3

4-3-2
L-D-R
Rear Axle

that example. (again working in a series in 4wd)

and thats what causes the steering to go funny, The cars wheels are trying to follow the tracks as they are setup in accordance with the ackermans principals but they cant because the mechanics of the drive line want to haul it all back into a straight line.

[Panda]

Thanks Dave ... :)

[V8Ian]

Very well explained Dave, do you teach this at work?

[Blknight.aus]

ya welcom

[Blknight.aus]

Very well explained Dave, do you teach this at work?

only to people who want to learn.

[V8Ian]

only to people who want to learn.
We do and have, thanks mate :BigThumb:

[isuzutoo-eh]

Originally Posted by Blknight.aus
before we go on with the next bit go grab a normalish size vehicle (one with 4 wheels about the size of say a landrover 110/109) stick it on hard lock and drive in a slow circle on some sand, a wetish track or really clean cement, the objective is to leave tracks.

you'll notice you have 4 seperate tracks counting from the inside out they will be

the inside front wheel
the inside rear wheel
the outside front wheel
the outside rear wheel.


Not that it changes the meaning of life,
'cept won't the rear wheel tracks be inside the front wheel tracks:
the inside rear wheel
the inside front wheel
the outside rear wheel.
the outside front wheel
..because the rear follows the front on the shortest path possible?

Then again its 3am and the mental gymnastics hurt.

:question:

[Blknight.aus]

errr, hang on... I'm digging out my books now......


ok, it does change depending on your vehicles geometry and steering system. And I've got it tail about....

the longer your wheel base and tighter your turn the closer the rear wheels get to the center.

articulated and multi axle steer vehicles follow the example I gave and your on the money for a normal vehicle...

[Panda]

Ahhhhhhhhhhhhhhhhhhhhh :wallbash::wallbash::wallbash:

My mental capacities have been hurting since the start of this thread! :D


Not that it changes the meaning of life,
'cept won't the rear wheel tracks be inside the front wheel tracks:
the inside rear wheel
the inside front wheel
the outside rear wheel.
the outside front wheel
..because the rear follows the front on the shortest path possible?

Then again its 3am and the mental gymnastics hurt.

:question:

[Blknight.aus]

no need to get twisted up about it...

what I've gone and done is mixed up the angular direction of the wheels with the paths of the wheels

The basic principal of the detroit causing steering problems by driving the front diff at the wrong speed is sound and I would have picked up on my error if Id been using real numbers instead of simple made up ones.

[Panda]

twisted up about it? You mean like the splines on the front axles?? :Rolling:

It's okay Dave, I was only messing with you ... don't suppose you'd like to enlighten me regarding LSD's in fast cars would you???

:angel:

[Blknight.aus]

well, if your driving properly they dont do a thing....

when you over cook it and a wheel lets go they ensure that some drive remains going to the wheels that can use it so you keep control....

same concept as a locker for a four wheel drive just faster and less agressive.

oh and when you say LSD did you mean

mechanical cone clutched?
mechanical spiral clutched
fluid coupled?
viscous shear coupled?
electrically coupled?
Band braked?

[Panda]

Hmmmm ... I'll have to get back to you on that one! :D


well, if your driving properly they dont do a thing....

when you over cook it and a wheel lets go they ensure that some drive remains going to the wheels that can use it so you keep control....

same concept as a locker for a four wheel drive just faster and less agressive.

oh and when you say LSD did you mean

mechanical cone clutched?
mechanical spiral clutched
fluid coupled?
viscous shear coupled?
electrically coupled?
Band braked?