Just bought a long wanted 300cd. Nice one with 133k and perfect maintenance by MB dealer. Driven conservatively by one owner. Everything great except car has light resonance/rythmic vibration at speed. Have replaced driveshaft center bearing, engine mounts, transmission mounts. Wheels are balanced. Local MB dealer says I need new driveshaft. My questions: how can drive shaft go bad on such a pristine vehicle? What else could cause this irritating vibration. Thanks. Nic in S.C.

I have an 83 300D and had the driveshaft replaced at 100K miles because of vibration problems. The dealer tried everything else you mentioned, but the new aftermarket driveshaft did the trick. As I recall, MB wanted about $900. for theirs but the aftermarket one cost me about $350. That was 60K miles ago and I haven't had a vibration problem since. Not sure how a driveshaft gets warped/bent/out of round.
Good luck!

Before I spent the money on a new driveshaft I would take it off and have it balanced. That can be done for cheap and it will also tell if it is bent. The slip joint could be worn to. Just my 2c worth.

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82 300SD 100K
91 Caprice SS
92 Jetta TD