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I am experiencing same and have explored many areas. My dealer has another car in with same and they cannot pinpoint it. In my case, this occurs when I am leveled off at a speed 40 and above and there is no acceleration or deceleration. It is a noise that starts and then at one point becomes a warbling. It stops if I accelerate or, most of the time, on its own. It does not occur with acceleration or deceleration or going up hills and seems to only occur when the car is running steady at its lightest load. In my case, it is most obvious when listening into the drivers area where the accelerator is.

I thought maybe it was the flexplate but have changed my mind as there are different symptoms apparent with the flex plate. The flexplate issues are due to the fact that initial engines have the flexplate secured by rivet which loosens and causes that noise. The fix for that is to replace it and the bolts. It is handy to note that there is a TSB for this sound that suggests the flexplate be replaced if the sound cannot be pinpointed. There are cases with same sound after replacement in result. I also considered the torque converter and might suggest the person who states his vehicle becomes sluggish when accelerating look into that possibility. Tuned into this thread and it sure would be great to catch a great audio recording of the sound...its a hard bugger to nail down though.

Oh FWIW, I just finished a trip running the hell out of the car out east. I think we put on about 600 miles. The sound was there before and is still there. It does not appear to affect any functionability of the car, and as well does not affect the mileage as I hit 27mpg at one point during this trip for the first time EVER!
 

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Allflash,

I did post a YouTube video/audio clip which GM Corvette Quality Management, and their Exec Mgmt have seen. In case you didn't see it, here's the link:

"Warble" noise heard on 2016 Corvette C7 A8 Trans. NPP Exhaust. Most noticeable at the 35 to 40 second mark, 1:09 to 1:18 min and 1:42 to 1:50 minute mark, and 2:35 to 2:42 minute. Can also be heard less noticeably through out when going up hill. Most always at 1500 rpm, regardless of V4 or V8 mode, or any other mode settings. Light pressure on the gas pedal.


I'm hoping the Quality Engineer coming to evaluate my car next week has sensors to better capture the sound, and more importantly, WHERE that sound is coming from specifically.
 

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I could be wrong but that sound seems different, like the flex plate which would cause exactly that sound as the rivets loosened. Your sound is like a "wop-wop-wop" which you can positively say is related to something spinning. Would that be correct?
 

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Allflash,

Yes, I'd say that's a fair assessment.
 

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I wish I could capture it but mine is more like a rattling sound under the engine...totally random. At one point it sounds like there is a marble in the mix... It is like a loose plate that isnt connected to a spinning. Still watching the thread closely though.
 

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IF and WHEN this noise issue ever gets resolved, I'm not sure what I'll do for entertainment anymore...... LOL !!!! I guess I'll go back to talking detailing and how much I love my chrome wheels... LOL
 

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I wish I could capture it but mine is more like a rattling sound under the engine...totally random. At one point it sounds like there is a marble in the mix... It is like a loose plate that isnt connected to a spinning. Still watching the thread closely though.
This is the sound I have. It sounds almost like detonation/pre-ignition. Mine happens under slight throttle application (just above what is required to maintain a cnstant speed). It usually happens between 1300 -1700 RPM. It doesn't happen if I disengage the AFM.
 

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Update: Took car in yesterday and installed new z06 shaft on drivers side. Did nothing, still have the noise. SM to get back with Detroit Eng. and figure out what plan B is.
Since the change of the half shaft did not fix your problem as GM surmised, I will again say that such noises, which appear at a constant RPM in various gears but not a constant speed, should not be in the drive train anywhere from the wheels back up through the shafts, the rear differential, and the output side of the transmission.

This has been discussed on other threads, but I am just writing it again here as an attempt to help when you talk with the engineers who are sent to help diagnose your car.

I still wonder if it is in the drive train at all, or if it is somewhere else.
 

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Chrome wheels, yes me too. But actually have to admit my adrenalin red seats and console give me a h-----n. Bringing in car to csr svc this week to address the WARBLE issue.
 

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Muzzy, and anyone else who has recently joined this thead:

For those of you recently joining in on this thread....... and it seems like it a a fair number of folks....PLEASE PUSH BACK on your Chevy dealer on this. They need to get your car associated with this already elevated issue that has the attention of GM Executive Management, and Corvette Quality and Engineering so that can clearly see that it's many cars involved.

Tell them to pull up my VIN # 1G1YD2D73G5115594 as there is a Case # associated with this. Tell them to look up my You Tube posting of the video/audio clip of the WARBLE sound. The title of the YouTube is: "2016 C7 Corvette Warble noise".

bjones7131 (who coined the word WARBLE) has two case #'s on his car VIN # 1g1yb2d77g5120061.

My car goes in Wednesday morning to meet with the Corvette Quality Engineer (may be the Quality Engineering Manager) to get both half shafts replaced with Z06 larger diameter ones. Hopefully this is the fix..... we'll see soon enough.
 

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I don't see any signs of lugging, or the transmission not down shifting quickly enough. I can drive in Manual in 4th, 5th, 6th, 7th, or 8th gear and different speeds and get the same WARBLE sound. The constant is it's always about 1500 RPM. Does not matter is it's in Manual, or Automatic, in V4, or V8, or in any of the different drive modes. Also does not matter if the exhaust is set to track, stealth, or anything else.

For most of us with this "Warble" noise, it's being at about 1500 rpm, light foot on the gas pedal, and best if on an incline of any amount. Take your foot off the gas, and it immediately goes away.
Strake, if the constant is 1500 rpm; then how come it does not do it when you traverse the 1500 rpm in 1st, 2nd or 3rd. Have you tried that? I have noticed that in 1,2,3 there is always enough torque on the wheels to accelerate the car regardless of mph. But from 4th and up there always seems to be a combination of mph and gear # that will take rpms down to about 1500 rpm and warble if you try to accelerate slightly out of it. When I'm going at sweet spot (mph+gear) to recreate the warble (or perhaps bitter spot) and accelerate slightly and increasingly I notice the following:

In "D": Car gains a bit of speed until rpms get stuck about 1500, transmission still has not downshifted at this moment, warble starts. As I keep slightly pushing the pedal angle keeps changing but nothing happens it is like a small dead band on throttle input, transmission still has not downshifted at this moment, warble continues. Keep pushing pedal until you notice a somewhat rough and late downshift, rpms go up, car accelerates as it should and warble stops.

In "M": 4th or higher at certain speed for each gear, the higher the gear the higher the speed at which it will occur. Car hardly gains any speed, warbles, you keep pushing pedal until sometimes warble becomes a humming very loud, always makes me think I'm lugging the engine, you can feel the lack of torque, and this exactly what I feel in D before it downshifts.

Approximate Speed-Gear combinations for warble (which also take rpms down to 1200-1500 rpm):

~20 mph in 4th
~29 mph in 5th
~36 mph in 6th
~43 mph in 7th
~57 mph in 8th

Coincidentally, those speeds listed above to recreate the warble are almost identical to ones at which the car will downshift by itself even in "M" mode, i.e at about 20 mph there will be a 4th to 3rd downshift if you are decelerating.

Are we talking about the same issue?

BTW, I'm very happy GM is taking care of this. Thanks for keeping the issue alive.
 

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Manta,

Yes, I would say you nailed it...... and yes, I've tried to use Manual in 1st, 2nd, and 3rd to hear the noise, but it's too difficult to keep the car at 1500 rpm at low speeds...... as you described, the car has enough torque to power it up in speed.

Taking my car in in a few minutes. Hope this fixes it.
 

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Strake; did you see post #35? The half shaft replacement did not work for bjones. If it works in your car, I'll be glad its over for you, but sad that we might all be taking about different issues. Good luck no matter what!
 

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Manta,

Yes, I am aware that swapping out the driver's side half shaft did not solve the problem for Bruce in SC.

I just spent an hour with the Quality Engineer who drove here (Gettysburg) from Detroit, in his company car, Z06 ...... he is an acoustics Engineer, and spent considerable time analyzing my Video/audio clip I put on YouTube recently. He is also the same Engineer who went to Iowa last week to work on a Base A8 Vert with the same noise. They put on just a driver's side axle on it and it took care of the noise. He said my car was 10 times WORSE after riding in it with me. He described that the harmonic resonance is setting up at 360 hz. The vibration is going through the entire drive line and into the differential where there is possibly an internal part shifted slightly setting up this vibration into the driver's side axle..... as it gets to the axle and picked up by the surrounding structural suspension members it makes the noise we are hearing.

He brought with him some sound / signal measuring, analyzing electronic equipment along with high tech microphones which he will put on first and take measurements. Then replace the driver's side half shaft, then re drive and remeasure the harmonic resonance noise. They will replace the second shaft (passenger), if needed. I told him I would prefer they do both, if doing one.

I also saw in the trunk of his Z06 both the base axle, like on my car, as well as what they are replacing it with, a Z06 one...... it is significantly bigger and heavier duty.

As for my questions regarding LUGGING due to the very tall final drive ratio of 2.41 and that the Z51 cars have a 2.73 that may play into why we aren't seeing the noise in Z51 cars..... When I asked about Z06 cars, he pointed out that ALL Z06 A8 trans ALL have 2.41 final drive ratio..... same ratio as the base.

I really connected with this Engineer and he spent all the time I wanted with me and answering questions..... he rode with me in the car for about 15 minutes and heard the noise big time.... We're on the same page. He was brought into this whole thing about 2 to 3 weeks ago, after the emails to CEO Mary Barra and seeing and hearing the video /audio clip. He assured me that they will make it right, even if it means buying my car back if they can't get it right. I will likely get an update late today and pick the car back up again tomorrow morning. They had a loaner car for me as well.
 

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Thanks a bunch for the update. They are on it big time, they are going to get it sooner or later. Mine is a base too (2.41 ratio). Please let us know as soon as you get those half shaft replaced.
 

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Warble friends:

Well, my car has been at the dealer all day and my wife and I stopped by to see how it's going about 4:30 pm..... I spoke with the GM Engineer and they had NOT replaced anything yet. Spent all day doing analysis work from driving my car with acoustic sensors placed strategically. Apparently, they felt swapping out 1 or both half shafts before knowing for sure that it would resolve the issue would add not any value.

I received a call moments ago (8 pm ) from my Service Advisor who stayed with the GM Engineer. They asked me to come in at 8am tomorrow to discuss the situation. I asked if they had made significant progress to get to the root cause and the response was they wanted to talk tomorrow morning. I don't believe anything has been changed out yet. Who knows, perhaps they'll have a pleasant surprise for me .... all fixed, but....

Not feeling so good at this point.....

update to follow again tomorrow morning. If they are no further along, and stumped, I am going to encourage them to buy my car back and I'll get a Grand Sport. From what they said today, my car was VERY consistent exhibit of what the WARBLE is all about. They hadn't seen one this "good", or "bad". If so, take it back to Detroit and use this perfect example to figure out a long term fix for the hundreds, or thousands of potential other customers....

Richard
 

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UPDATE:

Well, I spent a very informative morning at the Chevy dealer with the Lead Development Engineer for Vibration and noise here from Detroit as well as the Service advisor. They spent all day yesterday, and into the night collecting data on my car, and it was still hooked up with about 30 wires to signal / sound analyzer and 2 laptops. NO parts were exchanged or removed. Got tons of data. I was able to view some of the data showing 3D sound analysis showing time vs frequency, as well as 2D showing the amplitude of the spike when the WARBLE occurred.

With all this said, it looks like there is a combination of several internal components within the driveline that are adding to the vibration which sets off the resonance noise. These components may be in the torque tube, trans, and differential and may be parts that are within the tolerance, but at the high or low side of the tolerance, or perhaps out of tolerance. As these tolerances stack up, in my case, it looks like it's setting up at 1500 rpm approximately this 360 hz resonance that is the sound we are hearing. This is one reason some base cars don' t have this issue, and other's do and to varying degrees. Mine is WAY worse than any other they have seen and done measurements on.

It looks like my car will be going to Detroit to be the one they tear down, component by component to examine the tolerances on the parts within, and replace the system component ( torque tube, or trans, or diff ) with a known good part.

Don't know enough details yet. They are certain that they will figure it out on our car, and then get the fix out. As I know more, I'll update, likely next week sometime.

Oh, by the way swapping a Z51 eLSD is certainly doable at their Proving Grounds Labs, but in the real world, isn't going to happen. When I asked about the Z51 diff he said because of the extra mass of it, it is likely helping to quiet down any vibration that has built up through the drive line.

Hang tight.....

Richard
 

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No car or vibrations specialist here, and not meaning to argue or be disagreeable, but those 360 Hz don't make sense to me. If we (owners of C7 with warble issues) are talking about the same warble then it would be a sound/vibration with much lower frequency, I'd say less than 10 fluctuations per second. 360 Hz means 360 fluctuations or cycles per second, it sure would not sound like what's on Strake's video which is what I was getting in may car too (or can still get w/ throttle controller set to stock). I'm sure we would not call it a warble if it had 360 Hz. If the forcing function for resonance has the frequency of the engine rpm's (1500), that's 25 Hz, it's still too high for what we are hearing.

Still, the warble is just the symptom and not the real problem. To me, the problem is that instant where the gas pedal changes angle and nothing happens (dead band) it is a control problem; hardware or software? I don't know.

So, Strake; are they buying your car back?
 

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Manta,

I too used the same math you did, but was corrected by this Engineer.... Engine vibrations get a multiplier applied, and I don't remember the term he used to describe it..... something like Level 4 ???? at any rate, I saw many detailed data views on my actual measurements in both 3 D and 2D and in all cases it WAS at 360 hz. I saw it on his laptop screen, over and over... This was also the same hz level that all the other cars measured at too.
 
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