I had a cat-back exhaust on my car for a while now, and last night I replaced the muffler. When I got the car it was stock and when I'd shift around 4K rpm or so I'd hear what almost sounded like a rattle or clanking sound coming from the exhaust. I figured maybe it's hitting a heatshield or the shield is loose, no biggie. I installed a cat-back with a Magnaflow universal oe style muffler, and the noise was still there, I didn't think anything of it. Last night I installed a straight-through HKS muffler and that noise is still there but it's real fricken loud, especially if I just rev the motor up to 4 or 5K and let off, so I'm led to believe it's something inside the exhaust. I still have the stock manifold and cat. Anyone ever hear this on their car? It's kind of annoying.
check all your hangers and shields....
we have many
LE61T PTE6262 Powered 
Yep I checked all the shields while I was under the car. They all seem to have plenty of clearance, even when I moved the exhaust around. The rear section was a little close to the tunnel so I adjusted the hanger a bit to pull the pipe more to the center. The hangers are all good and tight and I didn't see any other problems. The thing that seemed odd was that now that the exhaust is straight through, the noise got noticably louder. That was why I figured it's something inside the pipe. Maybe the cat or something. It's not even all the time. If I run the car out to 5K and shift without letting the engine unload too much, no funky noise. But if I let the engine unload, funky noise. And it's only above 4K. Below that I don't hear it.
put the car on jack stands , crawl under it
and have a friend rev it so you can find the rattle
[quote=97cavie24ls(JDM&00s/c sedans™)]put the car on jack stands , crawl under it
and have a friend rev it so you can find the rattle
Always gotta do things the hard way dont ya...
Oh, better yet, I'll put the car on jack stands, and make my friend crawl under it!
wussy , LOL
but then you dont get the pleasure of finding thenoise thats been driving you FREAKIN CRAZY
lol
LOL.. Tuche'. *takes a bow*
I had the same problem on my wife's Jeep. Turned out to be the cat. The catalyst had loosened up inside the casing and would rattle around. Sounded like a piece of metal rattling around in there. It was worse when it was cold. Dealer replaced it (twice) under warranty for that problem.
