I have been reading about a rattle in the new mustangs in the rear but im not sure if this is the same thing. I will make a long story short. I replaced the exhaust with flowmasters and bigger chrome tipesa little while ago. Once I replaced them I heard a loud rattle at around 35 mph when you have that deep sound comming from the exhaust. I thought it was my license plate frame so I took and padded that but I still heard it. I then padded the inside piece that covers the trunk latch but I still hear it. I then decide to get in the trunk and ride and discovered that it was comming from what appeared to be inside the spare tire. I thought maybe it could be the exhaust pressure is causing the metal to vibrate against the wood that lays under the carpet? Well i padded that too but i still heard it. I then took a sheet and laid it over the metal butI still hear it every now and then but it is not as bad. Im notreally sure what to do next.I was wondering if anyone has had this problem and if so how they fixed it or if anyone has any suggestions?

 

i installed my jba mufflers and now i get an occasional metal on metal rattle at low rpms. Its coming from the pass side rear but when i look at it nothing is rubbing and if i shake it with my hand i get no noise either. only thing i can see is where the metal nub on the hpipe slides into the groove on the mufflers its not all the way in. Its clamped good but i donno.

 

Two suggestions...OK, maybe three....

One, make sure your axle back clamps are as tight as humanly possible where they connnect to the over axle pipe. You gotta torque the crap out of them, or it will blow by, and sound like a rattle.

Two, make sure that one of the hangers onthe mufflers is not protruding too far toward the rear of the car, and contacting the frame. It will rattle like crazy....

Three, if neither of these correct the issue, the muffler is probably bad. I just had mine replaced at 16 months old. I had a constant rattle / hum right at 2000 RPM consistently.......Don't know how old your flows are, but this was a problem with the initial run of the AT mufflers....

Hope it helps,
Mike

 

i'm gonna try tightening the crap outta mine

 

Okay so I took everything out of my trunk (carpet, spare tired, and jack) and it is still has a slight rattle. Sometimes I can go for a few days with not rattle and then sometimes it does it often. The only real pattern I can see is: does it at low RPMS (never heard it on the highway), when I have people in the back seat it seems like it does more, and I have a nice little incline going into my work parking lot and it does it there a lot. I lifted my car and tightend the muffler clamps and checked to see if anything looked like it could be rattling but didn't find anything. The rattle sounds like it is comming from the rear drivers side. I am not sure if there is a way to check to see if the muffler is bad other then replacing it. Any suggestions are welcomed.

 

Quick question and it may mean nothing, but does it seem to make a difference when the car is hot or cold?

 

I had this same issue and found out it was one of my muffler hangers, the bolts was loose. Tighten down all your bolts on the hangers and it should go away.

 

I stand by my original post. Probably the drivers side flowmaster going bad. That's usually the one that goes....

Try smacking the drivers side muffler with a rubber mallet. If the baffle is breaking / broken, you may hear the rattle.....
or
Hold the RPM's right around 1900 to 2100, and have a buddy stand by the drivers side flow. Probably hear a kazoo sound.....
or
If available, swap the stock muffler back on, and give it a try. The above three steps are how I narrowed mine down......

Mike

 

um It doesn't really seem to make a difference.... I have heard it after driving the car around andI have heard it right after start up. I am going to put it on the lift tomorrow and look around again and try tightening everything up and hit on the muffler some.

 

i have the exact same problem on my flowmasters and i thought it was just me. it usually happened at idle like when im sitting at a stop light. i took it back to the place i got it done and they hit it with a mallet and all that and it never rattled. it mainly only happens when the exhausts are hot too like how Gman asked but i know that its because the metal expands. they tried a few different things like tightening but i still havent figured it out. still rattles at low rpms