Could be one or more of the u-joints in the driveline have jammed up. This happened to me recently. My rear suspension had been loose and getting worse...the classic volvo clunking upon take-off. Well, six months went by and I still hadn't replaced the control arms (aka 'dog bones' or torque rods) and I went over a speed bump at about 10 mph and it jerked the driveline so hard that one of my u-joints locked up. The rear end started making a terrible scraping noise even at very low speeds.

I replaced the torque rods, and the u-joints and I'm back in business. By the way...the torque rods went in easily. Just jack up the rear end and take one out and replace it...then do the other side.