My exhaust consists of Hooker headers, a high flow 3" Catco cat, and a 3" Flowmaster cat back. It is about a year old and I just started hearing a terribly loud rattle coming from the exhaust. I put it up in the air and checked every possible connection to the body. The entire system is welded by the way. I am positive that this noise is coming from inside the muffler. I called up Flowmaster and Summit and they both said that it was probably the cat coming apart and blowing it into the muffler. Anyone else have this problem? I am concerned because the system is only a year old. Thanks.

 

I had the same problem. It was the cat coming apart. If you tap places in the exhaust with a rubber mallet you can pinpoint where the loose parts are.

 

Check the heat shield on the headers. I believe that's what's called. My rattle too.

 

My cat rattled like hell. Turns out it was, like I figured, stuff inside rattling around. The bricks inside were busted up pretty bad, even though your cat is new, it might've taken a hit from a bump or something. When we cut it off, I shook at and chunks fell out. There also felt like there was a pound or 2 of dust inside my old muffler when I took it off last year, but that might have been its own rotted out internals. Here's one of the chunks of "cat brick" from the convertor:

 

I'm taking the car to my buddy's shop this weekend. We're gonna cut off the muffler and the cat and see what's up. I figure now would be a good time too to gut out the cat and run a straight piece of pipe through it, so at least it looks like I have one. I'll let you know what I find when the pieces are off. Thanks.

 

industrial vaccume

 

I had a pair of Car Sound cats, and they failed in less than 2000 miles. They also rattled like hell, and eventually the substrate that was broken rotated and clogged off the exhaust flow in one of the cats. They were changed out at 2000 miles and the warranty was useless.