Here is a real life example. Last winter I was driving behind the yard to look at some equipment. We had about 8" of snow on the ground with some hard drifting. Truck was in 4 high. Well I fell into a hole with the front tire. "stuck" I tried to back out but the truck would not move. Would not spin the tires on the frozen ground no matter how hard i tried to rock it. Truck would just sit there and stumble. It never quit running though. So I shifted to 4 low. Now it would rev sky high as I tried to rock it back and forth, tires spinning. But this isn't helping any as now I'm digging a hole with the rear too. So I shift back to high and try some more to ease it out with out spinning and keep my traction on the ground. Truck just keeps stumbling, but I am moving a little back and forth. After a while I finally roll out of this hole and drive away.
What is the problem here?