[schoenmaro55]

Hello Everyone,

I have a 2021 Camaro 2SS 1LE with a Manual Transmission. The car has 8k miles on it and runs great, EXCEPT for an inconsistent rattle that overpowers the whole car. It's not just some slight interior rattle, (because believe me.. it comes stock with plenty of those). This rattle itself overpowers the engine, exhaust, and can even be heard with the windows down.

The car has an aftermarket axleback exhaust the original owner put on it. I've had it at 2 different shops trying to figure it out. One shop put a bunch of dynamat material around all sorts of plastic interior trim which accomplished nothing. I had another shop estimate that the axleback tips of the exhaust were striking the bumper so they lowered the exhaust slightly to make sure that contact wouldn't* be possible. After all this and a bunch of money spent, the rattle is still the same.

It's most pronounced after driving the car really aggressively and can be head on acceleration, deceleration, and most pronounced in 5th-6th gear when the engine is bogged down (which I don't do too often, but it's a good way to make the noise come out).

I've had a couple people suggest maybe the rear window wasn't mounted right at the factory and maybe that's the noise? Also I can't get the noise to come out reving the car in neutral either.

I'm so lost and am open for any ideas. Attached is a video to show you the noise:

https://youtu.be/K-r0__d-u5M

Thanks for reading!*

[cam765]

Do you still have NPP even with the aftermarket axleback? Could it be the infamous NPP rattle?

[zxspeedspec]

Oooooh I have that same rattle. I'll be interested to see what this results in.

[SomeGeoffGuy]

It could be a loose baffle inside one of the aftermarket mufflers. That is more common than you would think. Corsa mufflers used to do that a lot back in the 90s when they first came out (they are much better now). I did hear one though and it was an absolute horrible noise - worse than your sounded on my tiny computer speaker.

You might be able to stick a broom handle into the tailpipe and see if you can make anything rattle. don't reef on it too hard, just wiggle it a bit, should be obvious if something is loose.

-Geoff

[Gunkk]

That sounds like buckshot inside a soup can taped to a Hitachi.

I'm with SomeGeoffGuy:
1. Bad muffler (loose baffle or weld dross bouncing around inside).
2. Bad install.
3. Some other head shield somewhere (top of trans, etc.).

[arpad_m]

My car had the NPP rattle (and I fixed it by applying the well-known TSB myself along with some Drislide), but what you have sounds way, way worse.

Don't think it's the NPP unless the valve is completely broken, which you should be able to easily verify visually.