transfer case grinds when

going into 4lo or out of 4 lo while stopped.

Its an 1989 k1500 wih auto locking hubs.

check for vacuum leaks, theres a vacuum switch that goes in the side of transfer case it should have 3or 4 lines running to it.....commain problum

My 91 z-71 does that but only if I stop the shifter in neutral between 4L and 2H. BUT if I change gears in one motion with out stoping in neutral it does not grind