I have a 94z a4 with built trans. My car randomly started making a weird metal knocking/chattering sound and when I had it on a lift sounds like its coming from the converter. Weird part is the noise is only present at idle in park,neutral,drive, or reverse. As soon as I give it any throttle the noise goes away. Any ideas?

 

Check the bolts that hold the converter to the flywheel and try moving it while your there in case the hub cracked.

 

i pulled off the dust shield and inspected everything the other day and everything looked perfect. all bolts where tight, flex plate wasent damaged. converter had no play. it sounds like nails are spining in the converter... is that possible and the fluid is clean and car runs perfect still?

 

Sounds like maybe you lost a vane or 2 inside. Would kind of make sense since at low speed you hear them and at higher speeds as centripetal force holds them to the case.

If that were the case, you could hear it better by rotating the engine over by hand.