2003 Chevy S-10 zr2 4x4 problems

I started having similar problems with my "03 ZR2, every once in a while when coasting to a red light or just slowing down it will make this grinding moise like trying to put an automatic into reverse while moving forward. It doesn't last long, I found out if I hit the gas, it clunks then the noise stops !
Do you think this can be the transfer case vacuum lock-out switch ? If so where is it located on the vehicle.  

I've got a 99 ZR2. I've had it since 99. Bought with 9,000 miles on it. I'm never hard on it and have also had lots of trouble with the front end. My wheel bearings went dry very early on. Replaced one when it had 28,000 and the other at 38,000. Not a good sound when those go, while making a turn. The most of my undiscovered troubles started when I had the torsion bars turned. Not sure if the other in here with trouble have had there torsion bars cranked also, but i've replaced 3 CV shafts since then. The angle is so steep with the front end up in the air. Only an inch higher but my mechanic seems to think that is my problem. Get this. I just put weight on the back of my truck cause i live in maine. put it in Fourwheel drive today felt just like front right was just engaging and disengaging back and forth. Front end pulled to one side. I took my weight off and it was a lot better. the weight on the back just pulled the front end up even more to a point where its stretched out too far.  

The ZR2 is supposed to have larger wheel bearings than the regular S10. The Wheel bearings on my truck that i put on are from an Oldsmobile Bravada. Wheel Bearings were identicle in appearance. Did they do the same for the Bravada, Blazers, Jimmys, like they did for the ZR2?