ok today we got the first heavy snow fall so i put my truck into 4 wheel and i pulled into my driveway and my driveway was on a hill so i put my truck into park and then i put the shift lever into 2 wheel and my truck rolled back like 5 feet so then i didthe samething and it did it agai. then i just left it into 2 wheel on the hill and it didnt move so i gave my truck a push and i stated to roll, anyone have a clue? it has 175xxx miles and runs amazing

Rolled or slid?

If it actually rolled, it sounds like the T-case is "hanging" in neutral (not going direct from 4 to 2 wd).

Is it a switch or is it an physical shifter on the floor?

Go to www.drivetrain.com they sell what is call a transfer case saver kit. it is for the dodge. You will need to check out the t case. the snap ring that holds the shaft in place comes off alowing the shaft to move back and forth. I think that is your problem. The shaft will damage the case if not repaired. Inspect your t case before buying any parts.

it a physical shift and it was rolling, my dad said it could still be in nuetral and it did switch into 2wd yet.