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!

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1986 300SDL 440,xxx