95 coupe had motor mounts installed drove it out loud bang shifting like loose

What is your question?

Changed trans mount , both flex discs , not sure discs were marked for position . Initial loud bang from rear like hitting floor board I'm 67 never heard this. The loud bang is down to a pretty good thump going into high kind of smooth 1st to 2 . Had it on lift yesterday not a Benz dealer but 60 year old mechanic with Benz knowledge. Put me in car raised lift fully put in drive at 1800 rpm pretty substantial thump in driver seat like something loose hitting floor board. Kept doing this over & over as he is under looking for movement. Had to drop rpm to idle for it to make thump at 1800 . He thought rear bushings put jack under rear same. Ultimately he said the u joints were it easier to replace the 2 piece shaft , I don't want to put new shat and have same thing. Lot of money . What about trying the center mount has not been replaced or bearing as it is called. My 95 has only 123,000 was as smooth as silke for 5 years I own it until motor mounts changed . Help please thanks

What makes this problem better or worse?

Flex & tras mount helped

How long has your 1995 Mercedes-Benz E320 had this problem?

6 months