Thuddng Sound When Driving in Reverse

Although it can be challenging to determine what is causing an issue with a vehicle, it sounds like the concern can be reproduced. A few questions that would help point us in the right direction. 1. How many miles are on the vehicle and model? 2. Is the vehicle a manual or automatic transmission? 3. Does the noise occur when shifting into reveres or any other gear? 4. If it happens in drive does it occur when the transmission shifts? 5. Does the noise occur when on a flat or incline surface? 6. Does the noise occur just once; or continuously when moving? 7. Does the noise occur when lightly applying the brake pedal? 8. Can you tell if the noise is coming from the front or rear of the vehicle? It would also be helpful if you could share what the dealer has checked when in for service, as there are many components that could cause this issue. A starting point is the drive-line which includes the transmission, axle assemblies, CV joints, etc. If the drive-line is verified, the next area to inspect would be the engine mounts and suspension. I hope this helps and if you provide some additional information I am happy to respond.