Hi all, a silly question maybe, but you learn by asking...

1989 lr 90 standard axels and tranny/gbox.

diff locks - when you engage the diff lock, what locks?

is it just the central diff? or just the axel diffs? or both???

if both then mine is foocked!!

sorry, just been annoying me trying to work it out without takin it all to bits!!

cheers.

the diff lock acts on the gear box not the axles, dont use it on road, or you will wind up the transmition, off roaf it will give you slightly better grip in the ****ty stuff, but nock it off after

just the centre diff locks with the use of the selector if you want lock your front or rear diff u will have to go for aftermarket set-up.

air lockers

yep as i thought. have been using it right, but seems a bit pointless if it doesn't lock your axels up?

bigwill said:

yep as i thought. have been using it right, but seems a bit pointless if it doesn't lock your axels up?

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Burt it does lock back axles together so you have to lose grip on one wheel on each axle before you stop moving...

lerk are you saying when standard diff lock is engage. If either one of your offside wheels loses grip, and then one of your nearside wheels, regardless of which one, your then get stuck. I think there is also another type of diff you can install. But as said post manufacture install job.

If you have got to the point where you need axel diff lock - maybe its time to get the winch cable out?

You can drive pefectly OK with the centre diff locked on tarmac. The fabled transmission "wind up" cannot happen as both axle diffs wont allow it. Mine has not come out of centre diff lock since this cold snap took hold.

HOWEVER if you also have limited slip axle diffs (very rare and normally not in LR axles) or locking axle diffs (expensive) then you need to be on the slippy stuff or you'll break something if they are engaged. Normally a half shaft or a prop UJ.

Its no good getting stuck then fannying around trying different gear/lock combos. Chances are once you stop moving you'll never get going again. The secret is to maintain momentum and not to get stuck in the first place. Forward planning and correct gear selection are the trick to good effective driving in extreme conditions.

it is really meant for when you go up and down steep slopes. All the weight shifts on one axle and the lighter one spins up. It helps stop this. I wouldn't recommend running your diffs in on road as there is no need the centre diff is there for a reason.

whats a limited slip diff then?
and hows it set up does it have smaller gearing?

with a limited slip diff, yer can put yer foot down in the snow and ice , wheel spin everywhere and not veer off an inch , it will keep you straight, a lot of the yankee pickups have them , dodge rams etc,

The main advantage of a limited slip diff is shown by considering the case of a standard (or "open") diff where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate freely—the torque transmitted will be equal at both wheels, but will not exceed the threshold of torque needed to move the vehicle, and thus the vehicle will remain stationary. In everyday use on typical roads, such a situation is very unlikely, and so a normal differential suffices. For more demanding use, such as driving in mud, off-road, or for high performance vehicles, such a state of affairs is undesirable, and the LSD can be employed to deal with it.

Shifty1962 said:

You can drive pefectly OK with the centre diff locked on tarmac. The fabled transmission "wind up" cannot happen as both axle diffs wont allow it. Mine has not come out of centre diff lock since this cold snap took hold.

HOWEVER if you also have limited slip axle diffs (very rare and normally not in LR axles) or locking axle diffs (expensive) then you need to be on the slippy stuff or you'll break something if they are engaged. Normally a half shaft or a prop UJ.

Its no good getting stuck then fannying around trying different gear/lock combos. Chances are once you stop moving you'll never get going again. The secret is to maintain momentum and not to get stuck in the first place. Forward planning and correct gear selection are the trick to good effective driving in extreme conditions.

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WRONG WRONG WRONG. Wind up can and does occur if you drive around on a high grip surfice with the centre diff locked, and that can lead to big bills.

I do agree though that it is best to engage diff lock before you loose traction, so that momentum is not lost.

Davec said:

WRONG WRONG WRONG. Wind up can and does occur if you drive around on a high grip surfice with the centre diff locked, and that can lead to big bills.

I do agree though that it is best to engage diff lock before you loose traction, so that momentum is not lost.

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iv had it me self, ended up jacking the front wheels and letting them spin it off, suprising how it does it really , somethings got to give in the end tho :doh:

Davec said:

WRONG WRONG WRONG. Wind up can and does occur if you drive around on a high grip surfice with the centre diff locked, and that can lead to big bills...

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Unless you drive around in tight full lock circles all day long it will never happen. If you've had problems it will be for other reasons - such as different diff ratios between front and rear or odd sized tyres. :doh:

Newer Chevy 4x4s have a fixed transfer box with no centre diff to save money and they drive just fine. The Tahoe does not even have a hi/lo xfer box - just permanent high range locked 4wd.

During my 12 years in the military SOP was to lock the transfer box in all multi axle drive vehicles at all times. In fact there were specific mods done the the xfer boxes to prevent them being taken out of lock. The only exception was tracked or half tracked vehicles which have their own set of problems.

If you think about it why doesn't a standard 2wd transmission lock up? It has the diff to compensate across the axle. Just because you push the available drive to the front and rear axles it makes no odds. The front diff will take care of the front axle and the rear diff the rear. There will be little if any difference in axle speeds between front and rear unless your chassis is made from elastic or as previously mentioned you drive around in tight circles.

Taking it further what if you had 6x6? The two rear axles do not have a diff between them but they work without problems. They have the capability to turn at differing speeds but "wind up" is not an issue.

I've only ever seen a catastrophic case of transmission failure once and that was because the bloke had all diffs locked and went from mud to dry tarmac at full throttle. He tried to take a tight right hand bend and the result was a shattered prop UJ. The fallacy that if you jack the vehicle the wheels wil spin to release the "wind up" is just that. All transmission components are made of steel. They dont stretch like rubber and then return to normal - they stretch and break once they reach their limits. Any release will be minute and probably lost in the slack in your diffs and gears. The wheels wont spin on their own.

I've driven more than 40k miles across Africa and never had problems.
The only issue I will concede is that tyres do undoubtedly wear quicker on the front axle than the rear. But this is so for all 4x4s whether they are in permanent diff lock or not.

Ultimately you make your own mind up. I drive in extreme conditions for a living and I know what works for me. I've owned Landrovers for more than 30 years and never wound up anything yet. Other than some of you on here

90truckcab said:

The main advantage of a limited slip diff is shown by considering the case of a standard (or "open") diff where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate freely—the torque transmitted will be equal at both wheels, but will not exceed the threshold of torque needed to move the vehicle, and thus the vehicle will remain stationary. In everyday use on typical roads, such a situation is very unlikely, and so a normal differential suffices. For more demanding use, such as driving in mud, off-road, or for high performance vehicles, such a state of affairs is undesirable, and the LSD can be employed to deal with it.

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thanks

I think I am right in saying that when you do engage diff lock the front wheels should be pointing straight ahead..... thats what I have been told. Anyone have any other views?

If you are moving, yes

MrJC said:

I think I am right in saying that when you do engage diff lock the front wheels should be pointing straight ahead..... thats what I have been told. Anyone have any other views?

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shouldnt make much differnce if yer stationary