Here's my busted Differential pictures...

[HummBebe]

Originally Posted by f5fstop

I haven't experienced what you guys have, but I'm really not too sure if wheel spin is the main problem. Imagine your front tires are both completely restricted against a large boulder, log, or in deep mud. You floor the engine, and the prop shaft has max torque that it can obtain with the 4-wheel drive system. The vehicle starts to rise, the case flexes, the pinion starts to ride up over the ring gear.
Could this be the actual problem? I'm just speculating here and trying to learn.

I think in my case, it is almost exactly what you described, with the exception, I did not floor it, but gradually increased throttle until I felt the vehicle begin to rise, BTM as well, to keep it from spinning or hopping over the ledge.