I own a 1992 Mercedes Benz 500SEL with 83,000 miles on it. It runs incredibly well. The problem I am having is the car has a vibration from 45 miles per hour up to around 65 miles per hour. At 75 to 80+ it seems pretty smooth. I have looked pretty carefully at the flex discs and they both seem to be in good condition - i.e. no cracks or other defects. I am mounting another set of wheels and tires today to see if this changes the vibration symptom, but I am not optimistic since the vibration seems to be fairly high speed - like what you might expect from a propeller shaft. Has anyone experienced this, and/or been able to correct this?

Many thanks,
John

 

have a look at your driveshaft couplings and make sure that all six bolts are still in each.

 

I have done that - there are 8 bolts, washer, locking nuts per flexible coupling. Two days ago I took all the bolts out and replaced with new bolts, washers and locking nuts from two flexible coupling kits I purchased (made in Germany). I really wanted to replace the flexible couplings but to do so appears to require removing the exhaust system first, and I thought it worth a try to replace and torque the bolts. The vibration is greatly reduced, so it looks like I may have identified the source. I have a vibration now from around 50 to 60, and it almost feels like the vibration that was coming from the propeller shaft tunnel is gone, and the remaining vibration is a lower frequency, so I am wondering if the tires are contributing. I will keep expermenting. Thanks for your help!
John