Driveshaft vibration on 240D / 123 chassis

[pdrayton]

My 240D vibrates at certain revs when in drive. It seems to vibrate more under acceleration and at certain revs, not speeds.

The driveshaft support rubber where the spline joins the next part of the "propellor shaft" (as the germans like to call it) about half way between the differential and the transmission, is cracked and I can push the driveshaft a good 1/2 inch up and down in the supports, ie the driveshaft doesn't seem to be securely held in the supports and looks like it could wobble or 'orbit' in the supports. However, I find it hard to believe that those little rubber supports (kinda like a CV boot) could hold the driveshaft in place at high revs.

Is it the center bearing (pic attached or see at http://www.partsamerica.com/ProductDetail.aspx?mfrcode=BCA&mfrpartnumber=106&parttype=907&ptset=A) that holds the shaft in place?

I am assuming this driveshaft movement is bad, but am not sure, since I haven't seen any to compare it with.

If this is bad (the drive shaft moving 1/2" in the supports) then how do I fix it? Replace the driveshaft supports? Replace the drive shaft center bearing?

I have read various posts on this and looked at the MB shop manual (see http://skinnerbox.steaky.org/Service/W123/w123CD2/Program/Chassis/41-200.pdf ), but am confused as to what to replace, and more importantly, what it is called and where to buy it from. There are a few places on the web to buy parts called Driveshaft center support bearing (pic attached), or driveshaft support bearing, driveshaft support or driveshaft centerbearing.

HELP! confused! And want to fix it! Also, might it be the flexplate? How would I tell?

Thanks, and help would be greatly appreciated. I've worked on a lot of car things, but never a drive shaft! Feeling intimidated!