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Question about Land Cruiser (1997) 4x4 system.

Draft Horse

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Nov 16, 2020
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portugal
Hello all!
I've created an account here because i am looking for some expert advice on a technicality relating to the 4x4 system on my Land Cruiser 90 series (1997) with manual transmission and 3L diesel engine, with only 130k km.
We are the first owners of the car when my dad bought it new in 1997, and since I've turned legal age to drive some years ago, I've been driving it most of the times.
Going straight to the question, i would like to have some clarity on how this 4x4 system works.
I have some surface understanding on how it works, how to use it properly and what not to do. Granted, this system is barely used on 4x4, only once a year maybe on the dirt roads just for maintenance (so it will not go for years without ever working).
Sometimes after driving straight for a bit on the gravel roads, when i put it back to H, or normal driving, (every time i change something on the 4x4 lever the vehicle is stopped with clutch fully depressed) the yellow light that shows the 4x4 is engaged, will take sometime for it to go off. After the fact, when i reached paved road, i felt the steering a bit heavier than usual so i knew it was not fully disengaged. I reversed back to the gravel road, turned around once on the gravel surface and tried again to put it on LL full 4x4 gear and drive it on 1º gear for a while (always going straight, its a long dirt road).
Approaching the end, i selected H again and the car drove at normal speed ratio and the light indeed had gone off and there was no resistance on the road to steering. All good then.
But because my mind is rarely put to rest, i decided once back home, to lift one of the front wheels and test it by spinning by hand. When not in gear it spins freely, but when i engage in gear, it doesn't spin. This got me seriously worried something is wrong with my 4x4 transmission.

Shouldn't the front wheels spin freely, no matter if it is in gear or not, as long the 4x4 capabilities of this car be turned off?
I posted here a photo of the transmission levels for clarification.
Thank you very much for your time in advance.
 

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ren

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uk
HI and Welcome.

Don't worry.

The system is permanent all wheel drive with a center locking differential. Forgive me for including some things you may already know but for on your smaller transfer case lever you should have the following...
LL = Low Ratio Locked Center Differential
N = Neutral
HL = High Ratio Locked Center Differential
H = High Ratio (Center Differential is Unlocked) for normal road driving.
When in H and you raised the front wheel in Neutral as expected it would spin but when trying to turn the wheel in gear the raised wheel's driveshaft tried to turn the front differential but the other driveshaft is connected to the wheel on the ground so that can't turn and the propshaft connects to the center diff where the rear propshaft goes to the back where again the wheels are grounded so they can't turn and also via the gearbox and clutch to the engine which you would have a job spinning with your hand hence no spinning of the raised front wheel. Other designs with selectable 2 rear or 4 wheel drive would allow you to spin the wheel as there would be no connection to the front prop within the transfer box when in 2 wheel drive or because they had free wheel hubs (or both) depending on the system.
 

Draft Horse

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Nov 16, 2020
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portugal
Hello ren, thank you for your time and clarification!
I'll be honest, for all these years of us owning this Land Cruiser, we could had swore it was 2x4 when in H, what a surprise haha.
So this makes a lot of sense now, I'm relieved it is supposed to be the way it is. I guess i was just paranoid because it didn't disengage for some reason while on the gravel road, and the center diff light does take sometime to go off sometimes so it is not a very good indication.
Speaking of the light, is it normal for it to take some minutes or even longer to go off when changing back to H?
 

ren

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No worries. People on here have been so helpful to me and it's nice to have the opportunity to help someone else.
We had a car for years and we were sat in it one time and my daughter who was probably about 9 at the time reached across and pulled down an extra mini sunvisor that covered the gaps around the rear view mirror and we had no idea it existed and must have looked straight at it so many times. Amazing what you don't realise sometimes.
I don't often need to lock the center diff but it may need a bit of slip to disengage so being on a lower traction, either slightly slippery of loose surface and turning the steering both ways a bit would help. If you hit the tarmac locked you will have more trouble disengaging as it will be under strain and that's not good. Certainly people have spoken of issues getting locking diffs to engage and disengage but I think it is more of an issue with rear locking diffs. Some people do circles. May be worth checking the transfer case oil for peace of mind.
 

uHu

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Also check that the tyres are of the same diameter. If there is a difference between front and rear circumference, the driveline will always be binding when the CDL is locked, and thereby impossible to disengage. If, e.g., one tyre is new, while the 3 are worn, then put the new tyre at the front; as you can always turn in a curve to make the fronts run a longer path, but never make the rears run longer than the fronts.
Otherwise, a bit of hard braking or spinning, (if required followed by a tiny bit of reversing) would equalise the binding forces in the driveline.
 
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