Here is my understanding of the pre-xdrive 4wd system.

Pre xDrive X's have a relatively primitive 4wd System, I think its almost the same as my old explorer. There are also early (2000 or 2001) X5's that do not have 4wd at all. Was the wheel spinning in the rear? or front?

If you have the pre-x drive 4 wheel then I think you should see two wheels, 1 front and 1 back move. The pre-xdrive X5's lack any kind of locking/limited slip differentials between left and right (open diff). There is a DSC gizmo that uses the brakes to act like a limited slip diff but who knows how well it really works.

So what I think this means is that if there is a slab of ice under one front tire, and one rear tire, and your car is at a standstill, you will most likely not find traction. The DSC locking diff might get you moving just enough to get momentum.

__________________
2003 BMW X5 Manual