I have a 2003 envoy SLT. Just wondering if anyone has had this problem every time I hit the slightest bump there is a rattle seems to be comming from the rear. I have checked the underside and it seems to be comming from around the rear bumper but I can't seem to pin-point anything.

Welcome to AF. Rear stabilizer links are the usual culprits.

Thanks, is this an expensive job?

They can be a PITA to get off if rusted, about 1.0 to 1.5 labor, Moog makes an improved replacement. $40 each.