Hello guys,
I was randomly browsing as a guest, and bumped into this thread. I had the same exact problem, so just made an account to share my experience.
My car is an Audi A4 B9 Quattro 2.0 TDI (S-Line) from 2016 june, purchased as used with 82000 kilometers (~50000 miles) at 2019 august.
From the beginning of the ownership, I used it as a weekend car, so it was usual for me to have the car sit 5 days in garage.
I started noticing this noise, at low speeds (especially between 40-70 kph). The more often I used the car the more prominent/loud the noise became, the more it was sitting in the garage the more quiet the noise became. It took me some time to realize this pattern.
I took it to the original dealership, they found nothing wrong, because before that day the car was sitting to long and the noise was too quiet.
I took it on a longer journey, and booked appointment to an independent car analyst company. (After few hundreds of kms, on the way home, the noise was very hearable even at higher speeds).
The analyst guys lifted the car up, one guy span the rear wheels by hand, and it the noise could be very well be heard from underneath the car (center) from the transmission. So they localized the issue is either with the transmission or the power splitter (the unit that sends power to rear wheels).
Having all of this info, I went back to the original dealership and managed to get a test ride with the "head of service" guy and show him the noise.
They admitted that this occurs time to time with the drive shaft of the quattro systems. The problem they said is that there should be some grease inside the drive shaft, but mine somehow got dried out. But the driveshaft itself is a "closed system" and they can't just open it and fill it up, so they replaced the entire unit.
After this driveshaft replacement, the car was fine. For a few weeks....
I returned to them by having another issue, knocking sound from front right at high speeds (that later turned out to be some imperfect chassis repair problem). They were completely unaware of whats happening, so they just replaced rubber-silents around the suspension, thinking it should fix the knocking sound. At this point they might have done other fixes they didn't tell me, because after I got back the car from this service the driveshaft noise (that is the topic of this thread) was completely gone.
2 months passed since, and the issue still didn't return.
I love my car, but sometimes it drives me insane. I am really starting to question the reliability of the B9 platform.
Hope I could help. Best regards,
Zsolt
... it seems like something is rotating and making constant sound in background like "iiiiuuiiiiuuuiiiuuuu". I belive you should be able to hear it during whole clip.
