Checked underneath and the sway bar bushings are tight as well as all the other suspension links. Suspecting the struts by process of elimination or the mounts. Car only has 37,000 miles and bouncing the back up and down doesn't show anything. Any other way to test them on the car? Since it happens when loaded, jacking up the back and prying up on the tire wouldn't duplicate the situation exactly. Rock Auto has name brand struts for only $8 and the mounts for $3 (wholesaler closeout) if I have to change them.