The '82's (and some others) had a third 'motor mount' under the center of the engine *just* in front of the transmission ~ it needs to be adjusted or it will telegraph nasty engine vibrations directly into the body by the tranny hump .

Quite often the rear tranny mount gets oil / ATF soaked and goes soft and allows the tranny's tail shaft to transmit vibration .

The correct fix here is to replace the two engine side mounts and rear tranny mount _then_ jack the car up and located the 17MM ATF bolt on the center engine mount and loosen it until you can lower or raise the "L" shaped center part until it's dead centered in the hole it passes through .

I was shocked when a M-B dealer trained Mechanic didn't do this after installing my tranny ~ the vibration was -so- hash my Sweet asked if I needed a new muffler or something .

Those that couldn't figure this simple thing out usually removed it, a bad idea .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

''

Thanks Nate! I belive I know the mount you're talking about, it's the 2 13mm bolts I had to remove in order to lift the engine to do the motor mounts.
It's hard to believe that such a flimsy little piece of rubber could transmit so much vibrations. But, I really hope you're right. It would be such an easy cheap fix...

Let us know how it goes please .

That simple little mount caused me so much grief, I couldn't listen to the radio, talk to my Sweet and so on .

The "L" needs to be dead centered in the hole it passes through .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Folks, reporting back here with more info on this issue. Your opinions are much appreciated.

I disconnected the t-mount as Nate suggested, and there was no change. I then went for a drive and obverved some facts:

#1: When I bleed the clutch, it will work fine for about 10 minutes. Then the pedal will get soft, fluid in the master cyclinder goes down, but every system is bone dry (brake pedal stays firm). This leads me to believe the slave is leaking into the transmisson.

#2: the harsh vibration is present and unchaging regardless of motion, clutch postion, or gear selected. It ebbs and flows with RPMs.

#3: When the car is coasting, with the clutch pedal depressed, and I select gears, I observe a rattling noise coming from the transmission. I took a video of this sound, and you can hear it very clearly about 17 seconds in: https://youtube.com/shorts/S0jTuFyUV14

Here's what I'm thinking is happening. Brake fluid has seeped into the clutch, damaging it and throwing everything out of balance.
In regards to that sound, hopefully it's a pilot or throwout bearing? If not, something internal to the transmission, which wouldn't be connected to the other issue. This issue is concerning because it only happens when gears are selected.

What do you all think? This is obviosuly a big setback so I'm trying not to be bummed about the whole thing.