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That's the same RPM range (1500 - 1800) that my M7 changes exhaust note under very light acceleration even though I have it programmed for track all the time. I'm thinking your exhaust is doing something.
 
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That's the same RPM range (1500 - 1800) that my M7 changes exhaust note under very light acceleration even though I have it programmed for track all the time. I'm thinking your exhaust is doing something.
My M7 does the same in Track mode. I believe the exhaust valves (even in Track mode) are closed below that RPM range to control noise while driving at low RPM, like while on the highway in high gears.
 
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Discussion starter · #23 ·
Thanks guys! Hope to hear something tomorrow from the Service Mgr.
 
Discussion starter · #24 ·
Ah, you have now produced the sound in two different gears at the same RPM... That makes this issue not so clear cut now...
I was afraid you were going to say that, Rodney. :)
 
I was afraid you were going to say that, Rodney. :)
Yet, I am still hopeful that this will be something easy for them to fix. It might just make the diagnostics more difficult, but they are experts with the ability to hook it up and read the codes.

Best wishes, and let us know how it goes! I'm sending some positive vibes your way.
 
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Discussion starter · #26 ·
Yet, I am still hopeful that this will be something easy for them to fix. It might just make the diagnostics more difficult, but they are experts with the ability to hook it up and read the codes.

Best wishes, and let us know how it goes! I'm sending some positive vibes your way.
Thanks! Positive vibes and a drink for the nerves.:)
 
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Discussion starter · #27 ·
Well, even after a detailed description, dealer couldn't duplicate the problem, so I'll be making a trip down to do it for them Thursday. That's not a problem, but what I didn't like hearing was the suggestion that what I was hearing may be normal. :confused:
 
Discussion starter · #28 ·
Made it to Criswell today and was able to duplicate the howl I was hearing for their Corvette Service Specialist foreman, which was a relief. It is something that he has heard a few times before as others have described it as a groan or a whine. Feels 99% sure it is harmonic in nature with the drivetrain and exhaust combining to create the howl at a specific speed/rpm that is magnified at higher speeds. They went over every aspect of the car and assured me of no mechanical issues, also a relief. A report has been opened and submitted to Corvette Engineering and he will keep me abreast of any developments via email. As far as a fix, his best guess would be a future software update. If something here doesn't make sense, it was probably lost in translation, as reasoning and details were presented thoroughly and I left feeling a lot better than when I arrived.
 
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Feels 99% sure it is harmonic in nature with the drivetrain and exhaust combining to create the howl at a specific speed/rpm that is magnified at higher speeds. They went over every aspect of the car and assured me of no mechanical issues, also a relief.... As far as a fix, his best guess would be a future software update. If something here doesn't make sense, it was probably lost in translation, as reasoning and details were presented thoroughly and I left feeling a lot better than when I arrived.
I'm glad there were no real issues associated with the noise.

Harmonic resonance is a common NVH problem, and I'd bet we've all encountered it in one form or another.

Every part on a vehicle has a set of natural frequencies that it will "naturally" vibrate at (in the same way that a guitar string or bell has preferred vibration frequencies), and when two parts that are close or are mounted together have similar natural frequencies they can "harmonize". The amplitude of vibration (and the associated sound) will grow, as the parts vibrate in unison.

Since these vibration characteristics are inherent to the components, adding mass to shift frequency (literally bolting on weights in key locations) or adding damping (like isolation mounts) are the common fixes.

I don't see a software update being a solution in this case, unfortunately.

FYI - I worked for a Tier 1 supplier a decade back, and our team did nothing but design components to safely space natural frequencies in order to ensure no NVH issues occurred in production vehicles - it usually worked.;)
 
Discussion starter · #30 ·
Thanks Mobius! That makes a lot of sense in conjunction with what the Corvette Specialist said. I was pretty vague in my post and left out a lot of the specifics, but the part about the software update possibility had to do with tweeking the exhaust valve settings to change the exhaust systems harmonics at certain rpms. Of course, he's just making a guess at this point.
I just finished my break-in period and I'm pretty happy knowing that I won't have to worry about scattering parts under spirited thrashings, knowing what I'm hearing isn't a mechanical issue.
I have to say that I was pretty happy with my treatment at Criswell as well. When they first informed me of not being able to duplicate the sound, I thought "here we go," :( but when I showed up at a time of my choice, the car was sitting right there front and center with their best Corvette Specialist ready and waiting for me to give him a personal demonstration.
I talked to Supporting Vendor Mike Furman while there and he actually wasn't delivering a new C7. Weird. :)
 
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I bought a 2015 with the a8 auto and am hearing some noise in 6th,7th and 8th gear. This happens when im driving the car normal at 1400 to 1800rpm's, my dealer has had the car 8 days now and have no idea what it is.

Sometimes when coming to a stop it slams into 1st gear and the rear end is clunking

the noise was in 8th gear and then 7th and now is doing it in 6th, now have 1300 miles on car.

is also coming from the rear
 
Looks like you two have the same issue and I'm sure others have heard the noise with the A8, not sure why the Chevy customer service rep has not chimed in yet, maybe on vacation. Does the A8 tranny drop to first gear while paddle shifting and coming to a stop? All of my cars even my 2014 C7 and my wife's SS only drops to 2nd gear!
I thought that was a safety feature for the tranny not to start out in first gear while paddle shifting?
 
I bought a 2015 with the a8 auto and am hearing some noise in 6th,7th and 8th gear. This happens when im driving the car normal at 1400 to 1800rpm's, my dealer has had the car 8 days now and have no idea what it is.

Sometimes when coming to a stop it slams into 1st gear and the rear end is clunking

the noise was in 8th gear and then 7th and now is doing it in 6th, now have 1300 miles on car.

is also coming from the rear
Can any of the noises you hear in the higher gears be described as "clunk like"? If so, there maybe a tranny replacement required. There is some chance that a control module is failing, but I doubt it. Take it in and get your dealer to see if there are any fault codes stored. Keep us posted and good luck!
 
It's not a clunking noise. I hear it as a wow wow wow sound high low and high low over and over, I picked the car up today and dealer is saying its normal but i know its not. going to take it to another dealer and so on till I get it fixed.
 
I think I have the exact same problem. 1500/1800 rpm in 7th and 8th I hear a wow wow wow sound. Car only has 400 miles and its put away for the winter. Will be following this thread to get as much information as possible. Won't be taking the car back until Spring.
 
Discussion starter · #36 ·
I think I have the exact same problem. 1500/1800 rpm in 7th and 8th I hear a wow wow wow sound. Car only has 400 miles and its put away for the winter. Will be following this thread to get as much information as possible. Won't be taking the car back until Spring.
I have < 700 on mine and I'm probably in the same boat...80% chance of snow tomorrow. Maybe if there are enough open cases with the same problem, BG will be a little quicker to respond.
 
Also my NAV with PDR does not work. Way to go GM!
A bit of a mixed message, if you have a 2014 Stingray per your signature, "14 Stingray Coupe, Crystal Red, 2LT. Jet Black, Chrome Rims, Auto, Performance Exhaust, Nav, Z51 Spoiler. " you do not have a PDR. PDR was only offered beginning with the 2015 models.
 
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