Until yesterday, I had a vibration at 65 mph and above. After reading up on the subject, I suspected the flex discs and center bearing. Turns out the front flex disc had a crack between two of the bolt holes, and the center support was dried out, weak and cracked. I replaced both parts, put it back together, and went for a test drive. Now, no vibration at all even up to 90 mph. However, starting at about 60 mph there is a hum or whine. It gets louder when I hit the gas. Any ideas? I tried to mark and realign the driveshafts as best I could, but maybe I was off by one tooth on the spline...would this cause the noise?

Rich Mayer
82 500 SL

The flex disc only goes on one way. Did you install it the right way?
Sometimes when you get rid of one problem another one shows up. It could have been there all along but now you're looking for sounds and/or vibration so you notice it more.

Give us a bit more info about when you hear these noises.

The hum is gone. I got back under there and removed and reset the front driveshaft. My best guess is that I tightened down the 46mm nut before the driveshaft reached its equilibrium length, somehow causing it to bind along the way. Anyway, I drove at high speeds today and the car was very smooth and fun to drive.

Rich Mayer
82 500 SL