1996 Suburban transfer case problem

My 1996 Suburban SLT 4x4 recently developed a problem with the transfer case. I have the manual floor shifter. The case grinds in 2wd when I stand on the throttle. I put the shifter into 4x4 hi, low, or neutral, and there isn't any grinding.

Needless to say, I've been driving in 4x4 and I need to get this fixed! What could cause the case to try to engage while in 2wd? It seems like a bushing or something may have gone out??? I look underneath, no leaks, nothing noticeable...fluids are all good......

Ask this ? on the Chevrole Suburban side of this site. Some one over their will know. Dave

youre two wheel drive syscronizer is going bad