2002 gmc envoy_sle
I have this same problem too, only mine does it after traveling at highway speeds for an extended period (say 1/2 an hour or so). At first I thoguht it was the road surface but then noticed that it does it at other time and it also only does it when I turn the wheel and give it gas. I'm gonna change the diff. fluid this weekend and see what that does. Definately unnerving to say the least! BTW, I have replaced the u-joints and I have a G80 rear end.