Buzzing noise under load
Thread Starter
Safety Car
Joined: Dec 2006
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From: NC
2025 Corvette of the Year Finalist - Unmodified
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Buzzing noise under load
I posted in the Z section but maybe someone here has some ideas or past experience. My Z has developed a buzzing, noise recently. I noticed on a trip to the NC mountains a few weeks ago. It starts at about 1400 rpm and stops just over 1500 rpm and only in higher gears, like when the engine is under load. It seems to be coming from behind me. I've been under the car and looked for trans lines that might be vibrating , but saw nothing to concern me there. I looked over all the underside but didn't see any obvious issues. The car is an A8 and stock except for GM air intake, Mamo ported throttle body, and AWE X pipe. Stock exhaust. Any ideas that I could check. It's driving me nuts. 
Thread Starter
Safety Car
Joined: Dec 2006
Posts: 3,937
Likes: 1,925
From: NC
2025 Corvette of the Year Finalist - Unmodified
2024 C7 of the Year Winner - Unmodified
2023 C7 of the Year Finalist - Unmodified
2019 C6 of Year Finalist (performance mods)
Pads have less than 4K miles on them. Belt tensioner is a possibility but it's odd that it would only occur at that RPM range. It was suggested to check the X pipe connections. Visually everything appears good but I think I'll pull the tunnel cover and have a closer look. Thanks for the suggestions.
Drifting
Joined: Jun 2013
Posts: 1,291
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From: Iowa
Thread Starter
Safety Car
Joined: Dec 2006
Posts: 3,937
Likes: 1,925
From: NC
2025 Corvette of the Year Finalist - Unmodified
2024 C7 of the Year Winner - Unmodified
2023 C7 of the Year Finalist - Unmodified
2019 C6 of Year Finalist (performance mods)
Yeah, mine is not the "warble noise" as described in those threads. This sounds more like something vibrating against a shield or something. So I'm going to get under it and pull the tunnel cover and take a close look there.
Drifting
Joined: Jun 2013
Posts: 1,291
Likes: 363
From: Iowa
Is the noise coming from the exhaust? I think people talk about the AFM valves closing or something around that RPM. Perhaps it's that?
Thread Starter
Safety Car
Joined: Dec 2006
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From: NC
2025 Corvette of the Year Finalist - Unmodified
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2023 C7 of the Year Finalist - Unmodified
2019 C6 of Year Finalist (performance mods)
I guess it's possible. I checked the blades in the tail pipe and they seem to be tight. I'll do some research and see what I can find out. I have the AFM disable device so they shouldn't be in play.
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Thread Starter
Safety Car
Joined: Dec 2006
Posts: 3,937
Likes: 1,925
From: NC
2025 Corvette of the Year Finalist - Unmodified
2024 C7 of the Year Winner - Unmodified
2023 C7 of the Year Finalist - Unmodified
2019 C6 of Year Finalist (performance mods)
Pulled the tunnel plate today and inspected the connections with the x pipe. Everything was still very tight and as it should be. Nothing in the tunnel , X pipe area looked to be loose or suspect. Crawled back from under the car and bumped the passenger side muffler with my fist. I immediately heard the same sort of buzzing rattle. I believe it is something internal to the passenger muffler, maybe a broken weld or something like that. At least now I believe I have it identified.
Last edited by got2hav1; Jul 30, 2025 at 07:07 PM.
Instructor
Joined: Sep 2022
Posts: 119
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From: Peoria AZ
My '05 GTO had that same noise. Sounds like a metal clanking / buzzing and then it eventually turns into what sounds like a chunk of metal in a ton can. Mine was the driver muffler with a broken baffle.
I was going to suggest that and suggest looking at your AC compressor. My AC compressor went out. Started with the past few months with a whine and get louder and quieter with engine acceleration. then one day it turned to grinding. I thought to myself, please be an idler pulley or something else then the compressor. On my way home POW,! And AC is gone while on the freeway. Spent a day on my weekend doing a new compressor/ condenser / belt / tentioner
¡
I was going to suggest that and suggest looking at your AC compressor. My AC compressor went out. Started with the past few months with a whine and get louder and quieter with engine acceleration. then one day it turned to grinding. I thought to myself, please be an idler pulley or something else then the compressor. On my way home POW,! And AC is gone while on the freeway. Spent a day on my weekend doing a new compressor/ condenser / belt / tentioner
¡