I have a Suburban 1991, with some problems with the 4WD. It started last year, when I hear som real ugly sound when I used 4Wd, and made the wheels work a bit. I was sure that the problem would be the differntial in front, or the connections between this and the front wheel. It sounded like the noise came from this part of the car.
Because of this, I changed all the parts in front. Evrything from the gearbox and out to the wheels has been changed.
But the problem is still there.
I can drive easy and slow without any problems, but when i start accelerating a bit harder, or make a turn, the noise appear. It sounds just like it is jumping in and out of 4WD.
The problem is only with the frontweels.

Anybody who knows anything about this problem?
Thank you for all answers. I hope it is easy to fix, because we just got 1 1/2m snow, so I really need the 4WD...