This is a quick and dirty way to reinforce the flimsy center bushing that holds the rear drive shaft in place. over time this rubber bushing deteriorates and cracks causing a solid vibration in the center of the car. There are a couple ways to fix it.
1st-Audi Way. replace driveshaft for $1500 + labor
2. replace just the center bearing by pulling apart the driveshaft $130 plus lots of labor to remove driveshaft and disassemble the the center joint to replace bearing.
3. My way. it is cheap, and easy, and should work but if you have to buy a new driveshaft thats your call. I did this on my allroad but the concept applies to most other types of soft rubber mounts where a little added stiffness is required. It may work on your car but do not hold me accountable for any damages to you, your car, garage floor...
First off the driveshaft is a two piece design
and the bearing is in the center hence the name, but the bearing doesnot go bad the rubber support for the bearing deteriorates and looks like this
so I used an old trick from my days with DSMs and it was to fill the old mount with 3M Windo Weld
this is a single part urethane that is used to hold windshields in place and dries to make a firm durable rubber bushing yet will still flex.
so you will need this
1 tube windo weld
1 good chaulk gun
disposable gloves, vinyl or nitrile preferable
10mm wrench or socket
head mounted flashlight
then jack up car using a safe method, I used a ramp under the rear tire.
get a look at your bearing
now you know where it is you have to remove the heat shield, 4 10mm nuts hold on the heat shield, once off slide it out from above the exhaust and set aside.
no you can get a good look at it.
now for the messy part, get your gloves and keep them handy, I used about 8 sets
open thew windo weld and cut the tip to flow nice
apply the windo weld directly into the void in the bearing
you will need to smooth out the the windo weld with your finger and make sure that the upper part of the mount is evenly covered. work both sides until you have even coverage.
The thicker you put it on, the stiffer the bushing will be. I just made sure at it was even all the way around,
and then moved the driveshaft around to ensure that the windoweld had a good bond.
the acetone is for clean up, make sure you get any off the exhaust. it would smell real bad when it burns off.
replace heat shield and let cure 4+ hours preferably overnight.