The other day one of my favorite customer’s offers to take me out for a ride to listen to a noise he is concerned about, no problem. We pull out of the driveway at the shop and drives at a steady speed of 5 mph and he says, “Do you hear it? Right up front and I think off to the right, that strange noise” this noise was barely audible and if you exceeded 10 mph it would be completely covered up by road noise. It was a pulsating whirring noise that if it didn’t pulsate you would probably call it normal. If you parked the car for a time, you would have to drive it close to 5 miles before you could hear it again. Figuring out how we could duplicate it was a bit of a challenge and it took a number of tries and inspections before we figured out how to make it happen while on the rack and with us underneath listening. The culprit making the noise ending up being the center support bearing on the rear drive shaft between the transmission and differential. With someone familiar with the noise, sitting in the car and operating the gas pedal at the perfect speed you could hear the noise coming from the center of the car, not the front right corner as it seemed from driving down the road. A new Propeller shaft is the fix as Audi does not offer just the bearing. You might ask why go after a noise that you can barely here when more than likely it would get significantly worse and much easier to find over time. That is the difference between Preventative and Reactive service and repair. This customer has learned that waiting till something falls off is never the best way to go. In this case, the bearing would ultimately fail and we all know it would fail at the worst possible time and possibly causing more damage when it did completely fail.
In the video note how this shaft is above the exhaust and hidden on top of a series of heat shields all of which are susceptible to damage not to mention the transmission and differential with a complete shaft failure.