I have a 1998 Chevy Z71. When I put it in 4WD, if I attempt to make sharp left or right turns, the truck will lock up and refuse to move. I hear groaning and scratching sounds, but cannot locate the source. If I keep the wheels fairly straight, it drives fine. The only way to fix it is to take it out of 4WD and straighten the wheels.
I was given an opinion that the front spider (pinion/side) gears are broken.