While trying to diagnose my clunk into reverse, I have had the rear of the car (85 300D) up on jack stands. In trying to locate source of clunk, I ran engine and for short period had a loud thumping from , I think, passenger side front.
At moment, I am checking vacuum systems and started engine, just in Park. Again I had a thumping noise from passenger side front which gradually subsided after a few minutes.
There is likely more weight on front, but still haven't figured out what is thumping. The motor mounts were replaced 5000 miles ago and still look like new. At that time, the engine dampers and their mounts were also changed. All either OE or equivalent. Transmission mount just replaced (not OE

)
Anyone had similar thumping when rear jacked up?