Hey guys,

Car makes a rattling sound only when the car is in drive. The rattling will stop when the car is in park, which is weird.? Any ideas?

97 accord ex wag

 

Heat shield on the exhaust somewhere

 

Question is , why would it rattle when in gear and not raddle when parked.

 

Cus the the car will idle at different rpms thus causing different vibrations or frequency if it helps to think that way

 

The rpms remain the same. What heat shield are you guys talking about ?

 

When the transmission is placed into D4-D1 the engine will load against the transmission, this will cause the engine to rotate slightly. This can be witnessed by opening the hood, and placing the car from P to R or D. Or from R to D will show the most movement. When you are under the car with the engine on/off and the transmission in P there is no load on the drivetrain, this also does not rotate the engine which will also pull ever so slightly on the exhaust system.

Easiest thing to do would be to have a trusted individual in the car, and place the car in D4-D1 while holding the brakes, walk around the car and try to pinpoint where the noise/rattle is coming from. Slightly increasing the engine rpm while braking will increase the load and may increase the noise. You will most likely have to get on your gut to pinpoint the sound.

FWIW, when I installed the RS-R exhaust on the '95 EX there was a mass damper, looked like a large washer/bearing, that would make contact with the exhaust under load. Initially I thought it was the heat shield that bolted to the exhaust tunnel in the center of the car. This mass damper was located at the first 90° bend where the exhaust hanger is after the resonator.
When in Park the exhaust appeared to have plenty of clearance, but once placed into D the larger diameter exhaust would more closer to the damper, and under acceleration would make contact.

Look for loose heat shields on the catalyst, under the body, broken or missing exhaust hangers, broken, missing or stretched rubber exhaust hangers.