Yesterday I replaced the center support bearing, rubber mount, rear driveshaft bushing, and front and rear flex discs. Drove 275 miles - no difference
The bearing was little loose and I heard the balls spin around inside. The mount was cracked, but not enough for light to shin thru. that mount is VERY tough. I have seen (yesterday on a 76 450SL) mounts where the middle was completely separate from the mount, though. Three washers were missing off my old flex discs.
This may not apply in all cases, but in mine, I think unless the rubber fails miserably, it may not need to be replaced....
On the test ride, shifting into 3rd gear makes the ride a bit smoother. But not at 77 MPH. At 77, in '3' or 'D' there is something not right. I am pretty sure its been there thru several sets of tires, a new set of front wheel bearings, etc etc.
I'll have my tires checked on a GSP 9700 anyway, just to be sure. could be that something is causing all my tires to be chewed up a certain way