I finally got around to changing the center bearing on my 85'300D turbo with 165K miles on it. The bushing around the bearing was completely shot allowing the drive shaft to move at least a half inch in any radial direction. I carefully marked the shaft halves and the flex disk yokes on both the transmission and differential ends. After re-installing the shaft with new flex disks, I took it for a test drive. I now have a major vibration from the shaft starting at about 55 mph. Interestingly enough, the vehicle didn't have any noticeable shaft vibration prior to my replacing the center shaft bearing . I'm dumfounded on what to do next. Is it possible that the new flex disks have created an imbalance in the rotating assembly causing the vibration? Any help on this subject would be appreciated. Thanks!

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1985 300D Turbo California Model (134K)

These things just defy logic sometimes.

What sometimes happens is that the center u-joint wears a notch since there is so little movement. Resistance to u-joint bearing rotation at that notch sets up a vibration. SOME TIMES, you can loosen both carrier bearing bolts and remove one, the one on an angle rather than the one that goes in directly vertical. Then put a thick washer between the carrier housing and the body and then put the bolt back in place and tighten both bolts.

If that doesn't work, you probably need to get the driveshaft redone at one of the German driveshaft specialists like Beijer in Arizona.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Larry, I did notice that there was an almost "detent" feel that I felt in the U-joint bearing when I manually moved the joint. I like your suggestion which essentially (if I understand it) moves the U-joint to another neutral position that will hopefully be in a smooth operation position on the bearings. Is that what you're implying? I did ready a number of threads describing the difficulty of trying to replace the bearings, that were not designed to be sericeable. Are the flex disks a likely contributor to an imbalance? Thanks for your assistance.

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1985 300D Turbo California Model (134K)