I have an IRS and agree w/ u but anyway I've had 2 noises w/ stock shocks, first just a loosening connection from trailing arm to shock arm. Quick find. Second was shock itself, had maybe 1/8" play side to side on shaft coming out of the shock, didn't take much. It sounded like something was loose enough to make the entire rear end fall off and took a while to find. I was finally sure after taking it off and driving. Make you crazy, good luck.