[neon_rt]

What you observed is common with 4 wheel drive when the axles don't have a supplemental traction device such as a "limited slip" or "lockers".
You may have noticed that in a 2wd vehicle it is easy to get stuck when one tire gets in mud or on a slippery surface. It is the nature of the differential to apply equal torque to both drive wheels. If one wheel is on ice and it takes only a small amount of torque to spin it, the other wheel receives the same amount of torque (next to none). So essentially you resort to 1 wheel drive, the one that spins easiest. In 4 wheel drive you are driving both the front and back axle. The differential for both of them does the same thing as the 2wd we observed above. So if one back tire has no traction and one front tire has no traction, you end up in the same situation except that you are spinning one in front and one in back. Why a 4wd vehicle would ever be sold (or bought) without some sort of suplemental traction aid, I will never know. I got stuck with a Durango rental one time b/c as I crested the hill I was at an angle that lifted the weight off the right front and left rear tire and left them both spinning. Adding a "limited slip" or other device to the back axle will greatly enhance your off road traction. Some people put a device on both the front and back axle. My Cherokee has a Dana "trak-lok" rearend and standard open differential in the front. I've never gotten it stuck or even came close.