[apfubar]

Ulrich,

Thanks for the link, now I think I understand what is going on... It's just a byproduct of having a centre differential... If the truck stops on a steep slope, and the traction on the front wheels isn't sufficient, the rear wheels torque will be transferred through the centre diff to the front wheels.... The front wheels then start to slip, going backwards whilst the rear wheels roll down the slope.

To stop this you have to have a lockable centre differential.

Cheers,
AP