Date registered: Sep 2017
Vehicle: 1973 450SL
Location: Seabrook, TX
Mentioned: 0 Post(s)
Quoted: 33 Post(s)
Post-repair update for those researching similar driveline vibration issues;
I ended up taking the car to a really good Indy who only works on older Merc's.
The main source of the vibration ended up being the transmission mount and the driveshaft Centering sleeve / bushing. The transmission mount was not only very soft (almost gooey), it was the wrong mount. The mount was for a different year model and the PO had used spacers to make it "work". The rubber in the driveshaft centering sleeves were nearly gone as well. Those were the two main culprits. The center bearing was ok and the flex discs only had very few small hairline cracks showing up.
In the end, I had the new transmission mount installed, new flex discs, new center support and bearing, differential mount (soft as well), and host of odds and ends replaced. The rear-end was whining so I had it replaced while everything was apart. New steering coupler, rebuilt steering box, and rebuilt the power steering pump and added new power steering hoses. Now she silently glides down the road like driving on glass. Its glorious....although my bank account is still smoldering.