4wd problems

That's the one

Thanks guys, That's really helpful.

I have one final (I hope) question.

My stick shift T Box is off a Jimny, not a sami. so am I right to assume the prop shafts fit without alteration?
The only references I have seen to altering or swapping props around seem to refer to when sami boxes are used.
I just want to confirm what I think I know.

Cheers

That's correct. Jimny to Jimny is bolt on.

Roger Fairclough wrote: For future reference.

The greater the difference between tyre wear front to back the greater the "fight" between the axles because the wheels are being driven at different speeds.

The difference in tyre wear is completely insignificant compared to the difference in distance each axle travels when you turn a corner. Even with brand new perfectly matched tyres you will get wind up because we don't travel in dead straight lines. Any concerns about even tyre wear are misplaced.

Lets assume worn tyres 700mm dia. on one axle and new tyres 705mm dia. on the other.
700 x 3.142 = 2199.4 mm
705 x 3.142 = 2215.11 mm
This is a difference of 15.71mm in one revolution.
At 30mph, which is 13.41 meters per second, a wheel will turn approx. 6 times.
This means that in every second the difference between front and back axles is 6 x 15.71mm which equals 94.26mm.
In other words if you have a half shaft 30mm in dia. then every minute that half shaft will be twisted through 360 degrees.
If you are on a track that allows easy spin out to alleviate this twist, then all well and good but the moment you drive back onto a grippy sealed surface you must drop back into 2 wheel drive.
I agree that turning a corner will make things worse but to ignore straight line variations will not be tolerated by the transmission. Land Rovers are notorious for snapping half shafts and every picture I have seen of the remnants indicates severe twisting prior to breaking.

Roger

I can't fault your maths, but the point remains that turning induces a much bigger difference in axle speeds than tyre wear ever could. The simple fact is that if you use 4wd on high traction surfaces you WILL get wind up. On low traction surfaces then a difference of tyre size is of no consequence at all as the tyres will constantly be slipping anyway.
Every landrover since about 1980 has had a central differential, so the forces we are talking about simply will not exist (unless it is being driven with the diff locked). With a central differential you can run 4 completely different sized tyres with no mechnical stess on the drivetrain.
And of course a snapped driveshaft will always show signs of twisting. Twisting is the only means by which a driveshaft will snap. But there are multiple reasons that it could occur, and it's very unlikely that a variation in tyre size is one of them.