My 2000 GMC SLT Z71 just had a transfer case rebuild. Had new seals, gaskits, bearings, chains and fluid replaced. That solved the original problem of when at a low speed, 5mph or less the case sounded and felt like it was eating itself. It was loud and hard jerking. Once over 5mph it ran perfect. Shifting though the gears under normal acceleration and even full "pedal to the metal" perfect. Only at 5mph or less did I have the problem. I did limp truck home, luckely was only about 3 mile away and only had to stop once after I noticed the problem. Since being rebuilt with the new parts the original problem is fixed but I now have a brand new, never, ever happened before problem. When accelerating from a stop at around 35mph trucks seems to shift to neutral and the RPM's jump way up. Letting of the acceleraror for a second re-engages and I can continue on with no problems. It will do this several times but does seem to be less frequent when truck has been running a few miles and fully heated up. What could this be? The repair shop now says I need a tranny rebuild and I just don't believe that. I think there is something in the Trasfer case that may be slipping and they missed it and don't want to honor the warranty. What do yall think???