[cellardoor]

Hey guys, so I've had a 2016 RS V6 manual non-NPP for about 2 years. 6 months after I got it, the exhaust started making a buzzing sound when cruising around 3200rpm and 5200rpm. It would also make the sound when accelerating at low speeds. I took it into the shop, and after a few attempts of fixing it they eventually replaced the entire factory exhaust, claiming that it was a loose baffle.

Now a year and a half later, the buzzing is back. Same thing but worse - first few minutes of slow driving at low rpm's are fine. It seems to behave normally only when the engine is cold. Once rpm's reach ~4000 and you give it more gas, the buzzing starts. Any acceleration after this point causes the buzzing sound, regardless of accelerating from a stop, highway speeds, whether in gear or neutral.

This time, I figured I would get a new axle back since I've been wanting to change it up for a while. I went with the Flowmaster American Thunder. Good news: the mufflers sound amazing! Much better than expected. Bad news: the buzzing sound is still there, and of course is now amplified! For lack of a better description, it sounds like there's a full set of silverware jangling around in the pipes.

Here's a clip (hopefully you can distinguish the sound - it is much, much more pronounced than the video leads): https://youtu.be/xomCFMlaGbE

I've read many posts on here about rattling/buzzing/vibrating exhaust sounds, and it seems they all originated from different places. My plan now is to call my local chevy dealer and have them take a look at it. I'm hoping they'll take my word that this was happening before I installed the axle back (they have a strict policy stating they won't work on cars with any modifications whatsoever...)

Any ideas on what it might be? Among all the other similar posts, I haven't come across anything mentioning baffles.

[Rock-It Man]

Heat shields or muffler internal baffles. But so what? It's not going to affect performance or damage the drive train.

My exhaust started buzzing after a a few trips to the drag strip. Later it stopped. It's just sheet metal resonating. If it starts up again, no worries.

[cellardoor]

Originally Posted by Rock-It Man

Heat shields or muffler internal baffles. But so what? It's not going to affect performance or damage the drive train.

My exhaust started buzzing after a a few trips to the drag strip. Later it stopped. It's just sheet metal resonating. If it starts up again, no worries.

Lol I actually wouldn't mind if the sound was tolerable...this is so loud and shrill to the point where it's embarrassing. I've been turning heads, not because my exhaust sounds so good, but because I sound like I'm driving a weedwacker down the road.

I went underneath this morning and noticed some of the heat shield was rattling when tapped, so I tucked and crimped it a bit but after a test drive it seems that wasn't the source. I checked again this afternoon and tapped the exhaust pipes with a rubber mallet, and it sounds like beads are rattling around faintly inside...so I think it must be internal to the exhaust. I'll be calling the shop tomorrow to see if they can take a look

[speedup]

my NPP exhaust had a bad buzzing problem when accelerating from the valve not closing, they ended up replacing the whole exhuast

[Magna_Flow]

If you replaced the rear mufflers already and are sure that it isn't a heat shield, that really only leaves the catalytic converters or the center resonator as the cause of the sound. See if a shop can pop them off and take a look. They'll be able to tell right away if something is wrong.