andrews0915

So several weeks ago I put on my Flowmaster American Thunder single axle back muffler. The sound is great, but after a couple of days I started to notice that when I start it up and back out of the garage and then go down the driveway there is a pretty loud rattle. After I have left the driveway it usually is gone, and this usually only occurs when the car has been sitting for a while, so generally just the first time I drive it during the day. But in the past day or so I have noticed that it continues and is getting a bit worse. I don't think the bolts on the hangers are loose, I've checked, but the tip does move some, mostly up and down and it seems that this is because where the muffler clamps to the over-axle pipe there is much more movement than there was with the stock muffler. It seems that I mostly notice the noise when going at low speeds, and I'm usually turning and I seem to need to be in gear. Any suggestions or thoughts? Thanks a bunch.

760Mustang

If it sounds like a metal agaisnt metal rattle sound, check to see if the catback is on all of the way. All you need to do is hop under your car and check to see if the catback is pushed all of the way up until it meets a rivet in the midpipe. If it isn't, then that is most likely your problem. Loosen the catback and push it up to the rivet and retighten as much as you can to prevent it from slipping out unexoectedly.

Might be the problem, might not. Let's just hope you get rid of that sound as soon as you can.

Dex

maybe thats what my sound is. i keep getting it and i think it was after i took my pipes off to do the wideband

SaddleUp

I have Borla catbacks on my car and it did the same thing when they were first installed. Ended up being the metal hanger on the drivers side was a little bit too long and was rubbing against the inside part of the back bumper. Once the hanger was shortened (eh, about 1/2 inch) the rattle stopped.

Nuke

I'm having a similar sound when stock and which has gotten a tad worse since putting my FRPP Stingers on. I suspect a heat shield vibration. Seems to happen for me around 1100 RPM. I asked the stealership to look at it since I dropped it off last night for them to look at a few other minor things. I'll let you know IF they solve it (fat chance...).

yzfmik

I would bet that's the problem. My Loudmouth tips did the same thing as well as a bunch if others on here. It drove me nuts for like a month till I figured it out.

06elnr

I had a jba muffler do the same thing and it ended up being a baffle in side the muffler had come loose...now I have SLPs

bigray327

I had the same problem with my Flowmaster ATs, and just fixed it yesterday by re-seating the clamp. It didn't feel loose, so maybe since it's easy, you should just loosen it and re-tighten it, for grins. Worked for me.

I hate those queer clamps Flowmaster uses. I've read that a lot of people go use normal D clamps.

RdRang95

I had the same problem. It was one of the hangers welded to the pipe touching the hanger sleeve they slide into. When I installed my x-pipe stuff must have gotten moved around on my Loudmouths and caused it to run slighty. No problem to fix just loosen and readjust your pipes.

Rdot9

I have Magnaflows on my 6'er and i told the dealership to fix the rattle, i'm going to pick it up later today when my friend is back from getting his motorcycle license but i really really hope they fix it, it pisses me off, i hear the rattle everytime i slow down to about 40[:@]