Pegleg302

If the sound is happening when you are not moving, it could be a broken baffle in the muffler, or loose heat shield on the outside of the exaust system. I usually use a rubber mallet to tap on the pipes to isolate the source. Often a heat shield on a cat will start to rot away from its mounting points and make a really annoying sound. P.S. does it rattle at White Castle? sorry, I couldn't resist..........