hi I just put 315's on my 02 automatic and when I was helping a buddy I went to position my truck so we had light so I had to climb a small snow/ice bank maybe like 1-2ft and so I put it in 4hi when I got up to it and had the truck to the floor and I couldn't even go anywhere. so I used 4low. then the other day I had to turn around on the road so I figure id be fine with 1 front tire going through the ditch a little, but then in turned out the ditch was pretty steep so I went to back out and I got sucked in a little bit more, so I shifted to 4hi and went to back out but got sucked in a little more then I tried to rock It so after that I put it in reverse and floored it, all I seen was more soot than usual coming out of the exhaust and had no wheel spin, what would cause this? in 4low I can get them to spin, its like I have no power in 4hi, also I do have open diffs infront and rear if this helps. it just bothers me that I cant use 4hi sometimes. motor is stock just a superchips programmer on tow safe, and an intake and exhaust

this is how I was stuck, idk if u can see the pic but the rear drivers tire was almost off the ground, when I did get pulled out it did come off the ground about 6 inches I was told, just due to sway bars I take it.

 

It sounds like you need to take your t case apart and investigate a bit if your a pretty decent mechanic its a very easy process order a rebuild kit and a new chain i just did mine three months ago it was around 300$ for everything but i would bet your chain is streched and not leting it grab the gear for 4 hi