Flex Disc?
 

I'm relatively new at MB maintenance, but as I run into new problems, I'm learning. My 89 300se is having a vibration problem and have been told that I should replace the driveshaft support bearing and the flex discs. I have a couple of dumb questions. Are the front and the rear flex disc different or are they interchangeable? Also, not being a mechanic, I don't know what the purpose of a flex disc is. Any help would be appreciated.

The front and rear flex disks are not the same.

flex disks
 

I believe the noise and vibration reduction are a main purpose of using flex disks; takes a little of the jarring out of shifting too. I'm sure other's more knowledgeable than me will also address your question if I am wrong.

Flex disc on Benz is basicly the same as U-Joint on a Chevy. It is what connects the Trans. to the driveshaft.

On my W126 they are.

The front one usualy gives out first. Get under the car and inspect it. Replace the trans mount as well that usually cures a lot fo vibration problems.