W126 Periodic Vibration Source Solved
 

RE: 300 SDL Vibration at approx. 30 mph & then again at 55 through 65 mph.

Bottom line: Seemingly insignificant notch in U-Joint was the source. And I mean barely detectable / felt when I flexed it with it out of the car. Had the drive shaft rebuilt at Oceanside Driveline in Oceanside CA. $400 including all new MB parts (center bearing & carrier, end bearings / bushing, u-joint, & balance).

After months of searching and studying posts, and replacing motor mounts, trans mount, flex plates, center bearing / carrier, differential mounts, new tires, Bilstien shocks, rebuilt front end, MB alignment, shimming center carrier, etc. the vibration was still there. No joy......Finally just bit the bullet and took the drive shaft in to these guys who specialize in MB, BMW, etc.

Popped the shaft it back in and now at 387K+ miles she rides smooth as I remember when new. To be honest I had forgotten how smooth these cars can be.

Once again....Thank you members for your assistance along the way!

I had a seat of the pants oscillating vibration/rumble from about 35 mph up. Rebuilt ds solved it. When I took ds out, it was noticeably notched. I could feel it catching every direction I moved it. It was great to finally experience the smooth ride I knew it was supposed to have. My ujoint lasted about 275k.

Good to know - thanks for passing this information on (Posting is also a lazy bookmarking)

I had same problem, same solution at 320,000.

My local rebuilder said he cannot get replacement U-joints. And I thought I'd read that MB only sold shafts for my '83. Or maybe the issue was centering the U joint in the yoke. I guess I'll have to look into this again.

I wish you had said exactly what Vehicle you have.

There is a U-joint available for the W123s and several Years ago when I replaced the U-joint on Mine it was about $20 each for the new U-joint.

There is an old thread on replacing the U-joint
U-Joint 2005
http://www.peachparts.com/shopforum/showthread.php?t=124491&highlight=U-joint

My U-joint Repair thread 2011
http://www.peachparts.com/shopforum/showthread.php?t=293976
My Benz World post with all of the U-joint sources. Has some sources of the U-joint in it.
http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1581728-another-u-joint-driveshaft-thread.html#post4677977

Sorry. I have an '83 300SD. It was 2:30 am when I posted and I wanted to make sure I had a reminder to look into the U-joint again.

Thanks for posting the links.