So i'm new to the forum but helpfully you experts out there will be able to point me in the right direction. My a4 has started to make a noise The car is a 5 speed...recently the transmission was replaced and a stage 1 clutch and flywheel were installed (all done by ase mechanics) also the wheel bearing were replaced less than 500 miles ago. Just FYI. When I shift gears is when the car makes a bumping/grinding noise. The sound is coming from the rear center to rear right of the car. When the clutch is in the car is silent then when you let it out it bumps and grinds. Almost sound if a driveline mount is loose? It is loudest after initial shift and acceleration...when crusing it is almost silent. Also when floored at low rpms you can clearly hear it also. Any Ideas? Thanks

 

Most likely the driveshaft rubbing the frame when you shift or give it throttle. YOu want to check the rear diff mount which is located not far behind the driver on the passenger side. Look to see if there are any rub marks on the frame of the car just above where the driveshaft meets the rear diff.