Ok my buddy Jake knows a lot more about trucks than I and he showed me a neat-o trick. Ok, to get technical, the way a open diff in the back works is blah blah pressure is put on a clip which allows one wheel to spin crazy(the one off the ground) while the other wheel doesn't move at all. This sucks, I've gotten stuck in 4WD with tires off the ground like that.
Well! You can beat the design of axle! If you get a tire off the ground, and find your truck just won't @$%@$'in move because one tire is off the ground, you still have a chance!
Lightly set your ebrake, barely pressing it in. this adds pressure to the axles, fooling your tires into thinking they're still on the ground. This pressure of the e-brake puts pressure on the clip in your differential, making both tires turn instead of one.
Jus a lil tip
We tried this out on my friend Jake's 94 Dodge fullton truck, w/ open in the back. Then we tried it in mine, but couldn't get stuck haha. I'm glad :D