1990 245, M47

Symptom: Play in the rear u-joint.

I replaced my rear driveshaft u-joint with an OEM unit on Saturday. No real hardship - used a large hammer with a variety of sockets to be out with the old and in with the new. I checked the new u-joint after installing it (before installing the shaft), and found it to be pretty tight. Tight enough that it doesn't "flop" when I flip the driveshaft over (make sense?). I can move it with a small bit of force. No especially tight spots in the articulation - smooth all-around, but tight. Figured it might just need to "wear in" a little.

Installed the driveshaft in the car - drove it for several miles throughout the day and noticed a really low vibration - very "bass-y" - above ~25 mph. Seems to be a little louder when I put some torque to the wheels.

Took the shaft back out Sunday and made sure the flanges didn't look bent in. Smacked 'em a couple times with a hammer and brass drift. Still pretty tight - seems slightly looser (maybe..). Reinstalled, and drove it to work this morning. Same "bass" noise.

What's the deal? Are the snap rings too thick? I installed the driveshaft in the same orientation it was in before I removed it. Should new ujoints be totally "floppy", or tight? Could a new u-joint unveil some other driveline issues? The old one wasn't mortally wounded - but it was definitely on its way out.

I don't know. Very frustrating.