Checking the u-joint

[MPalm]

I have a vibration at 55-80kph and it sometimes gets really nasty, so I think the u-joint in the prop shaft might be bad.
I jacked up the car on one side to get underneath it and if I rock/twist the prop shaft back and forth w/ one hand on either side of the u-joint I can´t feel any free play but I do hear a tapping sound from it.
Could this tiny slack be enough to make vibration?
Does anyone know what size it is? The parts store didn´t have my car on their list

[GermanStar]

You sure it isn't just the driveshaft mount and bearing?

[MPalm]

The rubber disks are quite new and still fresh-looking, the bearing feels OK.

[Grubeguy]

If you feel it important to replace the center bearing, try Adsit Company, Inc. | New, used and rebuilt parts for Mercedes Benz automobiles

I've purchased a number of parts from them, and I've gotten lots of new stuff from eBay as well. Would you like contacts?

Before I sold my 114, I replaced the center bearing, and the bushing at the rear differential. I was floored at the difference in how it felt. The bushing was all of $5 extra...

[GermanStar]

No too sure why a gentleman from Sweden would want to order a $10 bearing he could get locally from a vendor thousands of miles away in Indiana....

BTW MPalm, if you do have a bad u-joint, you'll need to replace at least a section of the driveshaft, since the u-joint is NA.