m5board.comoholic (>1000 posts)
Join Date: Dec 2008
Location: Mequon, WI
Thanked 305 Times in 227 Posts
Thumping Noise From Under the Car
I need help diagnosing a noise that started a couple days ago and continued to get louder until I thought something was going to fall off! Over three days I drove back and forth to work which is like six miles round trip. At first I thought I had a small exaust leak, until I realized the noise changed speed with the car, not the engine speed. Almost sounds like something wrapped around the driveshaft and is slapping the bottom. Seems to be coming from right under the seats. I put the car up on ramps (still not a lot of room under there) and I can't see anything out of the ordinary. The drive shaft seems tight, and that bushing/joint where it bolts to the transmission looks OK as well. Wheels lugs are tight at each corner and I couldn't see any evidence of a broken mount. The frequency of the noise definitely increases or decreases with forward speed, so I suspect a rotating component, but I'll be damned if I can find it.
Any ideas? Clutch, transmission? I haven't got a look at the rear end yet, but that is next if I can jack it up.