2003 Dodge Ram 4 wheel drive trouble

I have a 2003 DODGE ST. CROIX EDITION 4 WHEEL DRIVE with a 5.7 HEMI engine. We have snow on the road's and when I am in 4w/d high and try to turn around in cul-de-sac at the end of street's my truck just stop's trying to go, it's like it is just jumping teeth or in a really bad bind. I can switch back to 2 w/d and it does fine. This only happen's in the turn's and seem's fine other wise. I deliver with my truck so each day I have this problem. The dodge dealer said he would have to tear apart the whole front end just to find the problem. I have done my own mechanic work for many year's but have never worked on a 4 w/d system. Sure hope you have a suggestion. Thank's a whole lot.
glen