I've got a 95 XJ with 140K miles on it and a vibration that is about to drive me crazy. It occurs at speeds of 55 and above. I've balanced the tires, aligned the front end, and changed the U-joints with no success. It feels like it's coming from the rear of the vehicle but I'm not certain because the whole vehicle shakes pretty good. Maybe some worn steering component? Could it be wheel bearings? How can I tell if wheel bearings are gone? What else should I check?