1990 Montero 5 spd auto free hubs. Driving in 4 HI, normal highway sounds. When I shift to 2WD, the 4WD does disengage, but sounds like the T-case is in 4 LO. Gears whining, but no grinding. When I get below 5mph, I hear a clunk and everything sounds normal. Put it back in 4WD and everything sounds and works fine