Hello; I'm hoping folks can help diagnose a weird noise that's becoming more common on my C7 A8.

Steps to reproduce:
- Car in Auto mode (cannot reproduce in manual mode)
- Get car up to speed, and coast at ~1300rpm (common at 40-45mph, 60-65mph - basically any time cruising around town or on highway)
- Nudge and hold accelerator to speed up (especially slight uphill grade, when car is under extra load)
- Clicking/rattling/clacking sound is heard. Seems to come from under car. No roughness is "felt" in car (no grinding, no catching, no shuddering).

I was able to produce for the service department at my local chevy dealer, and they were also able to reproduce on test-drives themselves. They described as a "tin -ey, metal on metal vibrating" sound, not likely coming from drivetrain. It was similar to an "exhaust-resonance induced issue" on another chevy truck, where a new bracket was TSB'd. The car was put on a rack, and "all stuff was checked / tightened", and inspected for rubbing/vibrating. Nothing found.

Car returned, issue immediately returned.

I used the PDR to record sessions, although the audio is pretty terrible:

Sound occurs at:
:01
:10
:18
:29 (long)
:36
:42 (long)
:54

Anyone have any advice? I'm actually trying to sell at the moment, and can't close with this issue!!

Thanks in advance!

 

Have they checked the belt tensioner? Common problem.

 

Didn't mention, so guessing no. I'll definitely pass along! Also for the layman, what is a belt tensioner?

 

Update - Dealer inspected belt and belt tensioner, and found fluid leaking from the tensioner, as well as slight cracking on the belt. New tensioner needed, and advised new belt. Both were replaced, and the sound seems to be completely gone! The car also seems to be down-shifting smoother (under low rpm; like hwy crusing).

 

Having this exact problem. What is the TSB for this?

Thank you for this post

 

No TSB that I'm aware of ..