Good replies you've received. If your driveshaft has a center support/carrier bearing assembly, it can often be a culprit, or an additional culprit; give's same sympromts. When I first got my 220D I knew my center support bearing was bad; but, the car didn't run, so I focused on that isssue. Took it for too many test drives as I got engine problems fixed. I could hear and feel the center support getting worse. At the point I refused myself to drive it again until I could bring it in to get it fixed (couldn't get assembly apart) I had already beat up the transmission (4-speed) output shaft splines. But, it seems that shaft is still very serviceable, so I am lucky. Check out that center support sleeve, bearing and rubber locater while you're looking at the flex disks. If the flex disks are bad and the center support hasn't been changed, there is a strong possibility the center support is on it's way to present problems. As difficult as it can be to pull those old driveshafts apart, it might be a good idea to change center support assembly, even if it seems not too bad of a condition.