I have a 97 A4Q 2.8 with 30K miles. I recently noticed a muffled banging sound coming from the exhaust when the engine is braking the car in 1st or 2nd gear. The first time I noticed it was last summer while decending Mt. Monadnock in New Hampshire. Can someone tell me if this is unique to my car or not? <p>Try this. Roll down all your windows (so you can hear more of what is going on under the car). In 1st gear slowly accelerate to 3,000 to 4,000 RPM and quickly let your foot off the gas. As the engine is braking the vehicle listen for any clicking, banging, or muffled backfiring. The sound is easily heard when driving next to objects that reflect sound such as a guard rail, building or a row of parked cars.<p>Does anyone know what this may be? Thanks.<p>-Tom Lazay

My 30V Avant is quiet, but I had something like that on old Coupe Quattro. Crawling around underneath and banging various parts of exhaust revealed that a heat shield that was riveted to the exhaust downpipe had broken loose, rattling and causing noise. 5 minute tack weld cured it.<p>Get under it and start rapping.