Binding up the drive train

[Alex Roux]

So this thread is for the more mechanically minded:

DawidT's thread on Reversing up an incline refers, and the mention made again of binding of the drivetrain:

I have searched the forum and the only other article that gives some explanation is on this one:
http://www.patrol4x4.co.za/viewtopic.ph ... ain#p28506

So I would like to give this topic more special attention

When in 4x4 (be that H or L), we should be careful how much wheel turn we do in reverse?
Especially on a hard (non slip type) surface.
This, I understand, is because the path length difference between the front and back axles is much greater when in reverse.
Why does having open axle diffs not resolve this?
Is it because the front and back axles are turning at different speeds, rather than the right and left wheels turning at different speeds, and us Patrols not having a central diff?

So does the winding up of the drive train not happen to the permanent 4x4 drivetrains - provided the central diff remains open?

Then my next question:
Just how much binding up can the car handle?
When in tight corners on a track, I sometimes wonder how much tolerance I should have for this.
I guess it is difficult to tell when on dirt, as the wheels do get to slip and adjust, right?

Thanks

Alex

[Peter Connan]

Alex, the front axle runs wider in a turn than the rear. Thus the two front wheels combined must turn more than the rear wheels combined. In a full-time 4x4 system with a central diff, the front and rear prop shafts can rotate at different speeds when the centre diff is unlocked, which solves the problem.

In fact, in a full-time 4x4 with all the diffs unlocked, you can raise any one wheel of the ground, put it in gear and start it without the vehicle moving. In our cars in 4x4, you need to lift one front and one rear wheel to get the same result.

I do not believe the problem is worse in reverse than forward, and I also do not believe a Patrol will break from this, even on tar. But it does feel and sound horrible and should probably be avoided as far as possible.