Landgruiser 100 centre diff lock.

Submitted: Tuesday, Dec 19, 2006 at 02:34
ThreadID: 123121 Views:2959 Replies:2 FollowUps:1
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Hi
Yesterday in hilly Gympie I had to stop at a red light on a fairly steep hill with a fairly heavy BT in tow. To get the rig moving when the light turned green I had to slip the clutch to the point where I could smell it.(NOT GOOD)
I have used low range before to tow it out of our driveway but this automatically locks the centre diff which tends to bind up even in a short distance. ( Requires a short drive in reverse to get the dill lock to disengage.) I have half worn tyres on the rear and new ones on the front which aggravates the bind up.
Yesterday I would have had to drive about 200 metres to the top of the hill in low range second before I could have easily started in first gear high range.
The questions are.
Does this bind up damage the drive train.
Is it possible to put in a switch which will allow the centre diff lock only to be engaged when conditions require it to be locked?
Is the centre diff locked when low range is selected because it is too weak to handle the load?
Ken and Aileen

Going walkabout - about time.

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Reply By: Ski Ali - Wednesday, Dec 20, 2006 at 08:53

Wednesday, Dec 20, 2006 at 08:53
Hello Ken and Aileen,
My basic and not proffessional answer to your questions are as follows. Firstly the centre diff on constant four wheel drive vehicles shuffles the drive from front to back as necessary. By having different diameter tyres on the front and back makes this diff work far more than is necessary and MAY lead to premature centre diff failure. The service manual says to rotate the tyres every 5000 kms to make sure that the tyre diameters remains as even as possible.
When the centre diff is locked, the drive train makes the front and rear wheels turn at the same speed and distance but turning corners or having different diameter tyres then the actual distance that the wheels travel is different. Something has to give. On gravel roads the tyres slip on rocks, sand etc and no wind up occurs but if the vehicle is driven on a tarred road then there is no slippage and the pressures created by having the front wheels travel a different distance to the rear winds up in the drive train. Slight wind up makes steering harder and as you say it is hard to get the vehicle out of four wheel drive. Tyres will scrub and in extreme cases damage can be done to axles, diffs and the ultimate failure is to have the transfer case split. Wind up is definitely bad for the vehicle.
In your case, starting on a hill and driving for 200 metres is something that you alone can decide. Providing you travel for a short distance in a straight line and the tyre diameters are the same then the wind up is not severe. (Not desireable but not severe). I know that these criteria are not always available. Driving with one set of wheels in the gravel is also acceptable as these wheels can slip. I guess (but do not know exactly) that it would be possible to put in a switch to stop the centre diff from being locked but my basic opinion is that someone with more knowledge on the subject than me decided that it is the way to go. I would not change it. Murphy's law says that the time you really need to have the diff locked the switch would be off and you would get into trouble.
I am pretty sure that the diffs on the cruisers are not weak. The thinking is that if you need low range then you need four wheels driving. You do not have four wheels driving if the centre diff is not locked.
Hoping this answers your question. Members with automatic gearboxes will probably be laughing at us members with manuals. I have ordered a BT and will find out about the clutch slipping later on next year.
Anyway, anyone with proffessional knowledge may enlighten us further.
Regards
Colin and Val
Merry Christmas to all
AnswerID: 569971

Reply By: Theywent Thataway - Wednesday, Dec 20, 2006 at 09:08

Wednesday, Dec 20, 2006 at 09:08
Hi Ken and Aileen,

I know this refers to an 80 series but it may well be the same setup.

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David.
the scruB ark...on The Way

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Follow Up By: Theywent Thataway - Wednesday, Dec 20, 2006 at 09:14

Wednesday, Dec 20, 2006 at 09:14
Hi all,
Just saw Colin & Val's comments and just need to add that there has been a problem with the 100 series diffs, particularly when put under any load in reverse and predominately the front diff. I blew mine at 5,000km while undertaking some basic driver training and it was replaced under warranty. I also know of the same problem with at least another handfull of 100 series.

David.
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