I,ve driven several 140 series cars that have an noticeable knocking in the rear of the car over washboard style bumps. Has anyone out there found the culprit and fixed it? The struts on a self leveling car retail for something like $800 a piece. Its an expensive problem to guess at. I've also noticed several of these cars that have failing hydro spheres. This might play into a correct fix. Your experieces would interesting to me as always.