Mercedes: E320 drive train noise and vibration, front wheel bearings, differential gears

Question
I have a '94 E320 with 230K miles on it and suddenly developed a drivetrain noise and vibration that increases with load and follows speed. Flex disks look OK. Axels seem OK and have about 1/2" travel inward but nothing radially. I can move the center bearing about 1/2" in each direction. No smoking gun, but also don't know what is accceptable play. Where do I go from here?
Thanks
Frank

Answer
There may be a bad u joint developing in the axel, or bad wheel bearing. Jack the vehicle so the rear suspension is free. With the vehicle in park rotate each rear wheel separately back and forth while someone holds the opposite wheel.
First rotate along the tread axis the free play first forward and then back against the differential gears. Listen for clicking sound in the axel U joints. Then hold each axel tube while trying to the rotate the wheel gently back and forth. feel for play in the U joints.

If the axel U joint are tight now facing the wheel hub place a hand on the front and rear of the tire. Try to push the right hand while pulling the left hand. Do this to determine if there is wheel bearing play.  Do the same process top and bottom.
If you have a ball bearing race that is broken you may hear some rattling. Also look for grease escaping from the bearing seal inside the wheel arm.

If none of these proceedures turn up a problem, I would also do the same check on the front wheel bearings.
Good Luck
Let me know what you discover.
Rob