clanking inside exhaust
 

I hear a loud clanking sound when I start my car up inside the exhaust system. It sounds like its coming from the part closest to the engine. It sounds like a nut or marble or a small rock is rattling inside on the initial start up when there is that first burst of air when the engine turns over. After that I can barely hear it while idling or driving.

check first for loose heat shields...

Could be a chunk of the cat. converter. Tap on the pipes and cat. with a soft hammer. Should hear it.