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Sounds like catalytic converter is possibly in little pieces. Might be parts of it in your muffler.

 

I don't think that would be consistently temperature dependent.

 

I think those mufflers use the preforated tube and glass filling like a Dynomax or Magnaflow. Its possible that the insides of the muffler are coming apart. When the metal gets hot and expands it might be moving around. On a side note, since I put my American Thunder system on my car, it makes the heat sheild for the gas tank rattle. I know thats not a heat generated noise but it could be a possibility.

 

I thought about that but it appears to clear the shield. What are people's thoughts on retrofitting a different crossflow onto the 5672 piping if the muffler is indeed bad?

 

I absolutely love my Flowmaster 53083 crossflow. Its not the usual one you hear on these cars. It has a much deeper meaner sound than the standard 80 and it won't fall apart on the inside.

 

Hmm it is in the actual muffler though? Only issue i have is under high rpm like on startup or under a load my back window rattles...could be 3" with no muffler and a high flow cat though

 

The only difference between the two are length, width, and thickness. Both have the same internals, I don't see how they would sound different

 

I'm definately not a fan of the flowmaster sound (or most baffled mufflers). I'm gonna bring it to a trusted shop here in charlottesville and have them find it. If it's the muffler I'll get a replacement edelbrock or another glasspack crossflow. If anyone has experience with metalic rattle sounds that develop as the car gets hotter please let me know. Other than that thanks for the input everyone.

 

53083 has the same insides as a 70 series big block muffler. Don't know how they configured it to crossflow but when you look into the inlet there is one of those small tubes that flow into sound deadening chamber and the actual exhaust gas flows down the center of the muffler to the V baffle at the other end.