I'm having trouble figuring out a rattling noise.

NORCAL

MEMBER
1994 AUDI 90
160,000 MILES

I'm having trouble figuring out a rattling noise that gets faster and louder with speed and not RPM. It sounds like it's just under the hood by the firewall and gets faster and louder the faster I go. It starts as I put it into 2nd gear and progressively gets worse. It goes away in between shifting and will diminish if I hold my speed just right on flat ground. Any acceleration or deceleration will cause the noise to become loud again. I was thinking speedometer cable at first but the fact it goes away in between shifting has me stumped. Engine performance is normal and there's no shaking or vibration. Just a horrible loud rattle. PLEASE HELP! Thank you in advance.

1 Reply

CARADIODOC

MECHANIC
33,871 POSTS

Push and pry near the center of the hub of the vibration damper to see if you can move the crankshaft forward and backward. If you can, the crankshaft's thrust bearing is worn and a counterweight may be hitting the webbing in the block. Also remove the inspection cover from the front of the transmission and look for metal filings.