A couple months ago I put in new rear lower control arms - upper arm bushings and shocks since then I had a slight thumping noise that gradually got worse. I have been under the car 4 times trying to figure it out.. I checked the torque boxes- exhaust - U joints. Torque on the control arms...... Finally today figured it out.. The upper nut on the right rear shock was not tightened all the way down. It would only thump on heavy acceleration or when tires started to break loose. Hopefully this may help others if they get the same issue.. I only drive the car on weekends but lately I spent more time jacking it up and crawling under it trouble shooting the simple fix..