Refresher: Symptoms, oscillating vibration through cabin when the car is in Drive or Reverse only. (vibration in steering wheel as well) When car is in Neutral or the RPMs are revved up in gear, vibration goes away.

The vibration has progressed over the last month so I've decided to tackle the problem. I used a stethoscope to listen to all elements of the serpentine belt (water pump, alternator, etc.) while the car was in Drive to listen for any irregularities (specifically the Tensioner). The Tensioner was the only thing that sounded off. Between Neutral and Drive there was a noticeable difference in the vibration of the pulley (random but subtle clanging sound) and the noise of the bearings. So I pulled the belt and the bearing in the tensioner clearly made noise and wobbled a little when I freely rotated it so I've decided to start with a replacement of the belt and pulley and go from there. My fingers are crossed that this resolves the problem.

I'll keep the board posted!

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1995 E420
1998 SL500 Sport
2009 E350 Sport
1995 S500 Coupe
1992 500 SEL