Yes, right around 1800 it happens for a brief second. I'll get under there tomorrow and look

If it is that, how do I fix it?

Try adjusting the flange bolts so the pipes move away from contact points.

I just got AAM Midpipe and Short Tails and Motordyne Art Pipes put on my car and I'm having the EXACT same issue.. I get that rattle briefly just under 2k rolling off from a stop, then it comes back around 3k and tapers off past 3.5k

Drives me NUTS trying to cruise somewhere on the highway when I have to climb up hill.

I gutted the entire rear interior and the noise persisted, so I'm certain it's something beneath the car.. That support brace towards the middle of the car that sits right under the mid pipe looks incredibly close, so I suppose at certain RPMs, it could just barely be making contact..

I'm out of town visiting my parents for the next week or so, so I don't have the means to get under the car right now, but dammit.. definitely going to try and get to the bottom of this. :ugh2:

if it was banging on that brace piece, surely there would be a hole or crack in the pipe where it had been contacting by now? or at least some tell tale signs.

Do you have stock cats?

My other guess is that it's just resonance in the piping. Get the car on a hoist with someone holding the revs at which it always rattles, wear oven mitts and grab sections of the exhaust to isolate the origin

No it doest make any holes or scratch on the pipe.
My resonators has been hitting that brace at certain rpm and does make that rattling sound.

Placed a nut bolt underneath the tower brace to lower it further down, the freaking rattling noise is gone.

To test...try pulling down your pipe if it does make contact with is this brace then that is the culprit.


Attachment 102565

Metal Rattle Sound
 

So the crossmember thing wasn't the source of my particular issue.

After hours of frustration I finally traced the noise to the inside of the rear fascia.

After taking it off :ugh2: I removed the white styrofoam filler piece inside the bumper and wrapped up a few of the wire harness/connectors with electric tape and stuffed a towel in there for "insulation" to further hold everything still.

Put the bumper back on and went for a ride.. No more vibrations.

I got on the highway and hit some speed and the rear fascia still seems solidly in place.. My guess is that styrofoam piece is just in there to "save" the bumper if someone hits you.

Nothing but clean mean exhaust note now.
Worth noting I took out the tools and styrofoam from the trunk also, and wrapped any plastic wire harness/connectors in electric tape in the trunk also. And also tighten up (don't overdue it and sheer bolts) any nuts in the trunk and inside the bumper.

you might want to put the styrofoam bar back in because it's an impact absorber. Think of a bicycle helmet - it works by breaking upon impact.

You're better off getting some EVA foam and wrapping the wiring and use the foam as padding to reduce vibrations

Metal Rattle Sound
 

Hmm.. Is it really a significant piece? Is it there for anything other than reducing damage to the fascia? Or is it safety related somehow?

This is the first time I've gotten desperate enough to take stuff apart off of a car to find the source of a problem like this, lol.

I may be willing to just accept the increased risk of irreparable bumper damage if that's all I'm creating for completely clean, rattle/hum-free exhaust sound inside the car.

I figure the car is so loud now anyway, no one is going to be able to just run up on me from behind without knowing I'm there unless they just happen to be deaf.. Lol

The foam isn't going to do much (if anything) to protect the bumper. As per juld0zer, it's there to protect you. Considering how little it weighs, I'd be inclined to keep it.

The styrofoam is there for a reason. You wouldn't take it out of the front (unless you need to to fit an intercooler, for example) so dont take it from the rear. Not sure what the laws are like in your area but you're more likely to sustain more write-off worthy damage in the rear than with the same impact to the front, styrofoam or not.

That aside, a piece of styrofoam isnt going to make the rattling noise you are describing. It's so light and has a soft surface so even if it was hitting something, the sound it would create is more of a dull noise. Take the towel out, wrap all loose objects with EVA foam (cut up a camping mat or old mousemat, old wetsuit or whatever - it's the black high density foam you're after) then squash it all back together along with the styrofoam piece. The more snug everything is, the less room for objects to vibrate and cause a nuisance.

There's also a thin metal heat shield above where the stock rear muffler would sit - that can rattle like a m*therf*cker but it never rattled on my car

Random rattle noise sound when I accelerate sometimes
 

Hey guys I’ve been hearing this rattle (like marbles in a can)/ticking sound coming from the engine bay sometimes! I try to make it happen again to record it but I can’t get it to replicate ! It happens randomly when I’m driving sometimes. It honestly sounds like when an engine rod/bearing goes bad. I checked my oil it’s good, it honestly hasn’t ever been low on oil so I don’t think it’s the engine itself. I had a muffler shop check the cats and they said they look nice (they used a camera). I honestly don’t know what to do 😭 or where to check!! My car is an automatic 09! Thanks

Litteraly been having this same problem on my car since I installed aam resonated test pipes, car had fast intentions car back for 3 year no problems, now it rattles louder than the exhaust at 3.5k every time I drive but it will only do it if the car is under load

OK! I have the fix!

Same problem. Same conditions. To my ear, the rattling issue exhibited the common sonic signature of an exhaust heat shield tapping against something that it shouldn't. You know what thin bent metal sounds like -- a resonance that's thin and brittle, with an odd decay to the sound.

The rattle was coming from the mid-underside of the car, without a doubt. My mechanic quickly found the culprit once the 2012 370z Roadster Touring Sport was on the hoist:

The heat shield on the gas tank was being struck ever-so-slightly by the brake cables when the car vibrated while in motion. He 'retensioned' (added additional tension) to the brake cables by simply pressing the brake cable brackets forward with the palm of his hand. No tools. Just his hand and moderate pressure to bend the brake cable brackets forward, thereby 'pulling up the slack' of the cables. Done. Fixed. The next day, I took it on a 400 mile trip through the winding roads of around Mt. Shasta and Mt. Lassen with no issues.

The annoying rattle is gone. Now, if I could get my mother-in-law to stop her incessant rattling.

Drive safe.
Stay well.