Like the title says a loud thumping that gets louder when in gear and at a stop. noise seems to go away at speed and when acceleration but returns during deceleration.

 

Check the rear transmission mount and also look at the center bearing and rubber isolater on the drive shaft.

 

The U joint is hitting the transmission tunnel due to probably wear/breakage of the center support bearing... Definitely in the driveline.

 

but im not moving in the video

 

Hm, well, right, nothing moving then, just reading it I assumed that other very common scenario... It's an engine noise then, possibly exhaust? I'm stumped, without seeing the car. Keep us informed!

 

could it be a broken motor mount allowing the motor to thump?

 

My guess is motor and tranny mounts. Check them. Perhaps your engine has shifted due to broken mounts and is vibrating against body somewhere.

 

other weirdness: acording to the vin and the dash it's supposed top be a turbo car. It sure doesnt have a turbo

 

good guess. i jacked up the transmission with the car in gear and the sound went away. now my question is why are there different mounts for the 940 and 740?

 

740's were from the 80s, 940's from the 90s, there was a constant evolution of enhancements over the nearly 20 years encompassing the two series.. 91/92 740's are mechanically *identical* to 91/92 940's.

I'd guess without looking it up, that EARLY 740's used a different mount than later 740's... and of course, automatics and manuals use different mounts.

 

according to my VADIS parts catalog, 1991 940s' only had two motor choices, the 16V DOHC B234F, and the turbo B230FT. The turbo used a AW71 automatic or M46 manual, while the 16V used the AW72 automatic (different gear ratios suited to the high revving 16V) or the same M46 manual.

now,t his just applies to US models, in the world market, there were undoubtably different configurations.