Highplains

I have posted previously about this problem in this and another forum but haven't seen this much discussion until now assuming we're all talking about the same thing. "Warbling" is about the best description I've heard although to me it sounds a bit like an exhaust pipe vibrating against something else. In my 2016 base care with NPP I've heard it since the night we picked-up the car. It has always occurred at 1500-2000 RPM more so if the engine is warmed-up. I have ruled out any differences with a Range Technology device which I bought for other reasons. In other words, it makes no difference whether its in 4 or 8 cylinder mode. I have heard it in reverse as well. I believe the shifting of the transmission to a higher gear or, as one member described, gently pressing the gas pedal at that RPM has something to do with the issue not because of the transmission but because the engine is taking a bit of a strain at that point (low RPM) and causes whatever to resonate. I think its an exhaust component and so does my dealer. When I took it to him with this complaint, he said they used a computer to shut-off the exhaust valves but this didn't change anything. Their demonstrator car did the same thing although to a lesser extent. He mentioned that Camaros, at one point, had a similar problem that turned out to be baffling in the mufflers. They found nothing loose in my car that would be vibrating. It interests me that one forum member had his exhaust or maybe it was just the muffler replaced and it stopped temporarily. It's also interesting that one member pulled fuse #32 and the noise stopped though he got the engine warning light coming on. This says to me that GM may have a bunch of bad mufflers on board.

He wants to wait and see what comes-up with other dealers and GM in the days ahead. This translates to me to, "We're waiting to see how many people complain." In the meantime, though annoying, my own opinion (and the dealer's) is that there's no harm being done. Unless it gets radically worse, I'll hurry-up and wait although I sure as hell want it fixed before the warranty runs out.

iclick

That should be at the minimum spec, and mine was at that level at first. I filled it just to maintain my OCD credentials, fully knowing it would make no difference at all.

I've never noticed any sounds like what's being described here in mine.

Mr. Stingray

Heard it yesterday on the highway..2016 1LT..Mag Ride A8..

bjones7131

Thanks to all for responding and updating this post. Lets keep this going until we or GM comes up with a fix. A 60+K car shouldn't make this noise. Maybe the customer service guy on the forum will read and respond. I sent them a PM and haven't heard anything. If we can get one guy and dealership to stumble onto a fix then the rest can follow suit. There is strength in numbers. Thanks again

seCen

Exactly. For the people in these problem thread other people are having saying their cars are so flawless or problemless, good for you...now leave it for the people who are actually having problems and wanting their cars to be fixed. My last car had one problem in the six years I've owned it and it cost a lot less than this vette so I'm expecting it at least the same.....When I get the problem fixed, Im expecting it not to come back but now it is or cause other problems to appear.

Arctic C7

Hey bjones - Drove to work in M mode this morning. Watched the V4/V8 light on the info display and it never went over to V4 mode, stayed V8 the whole 25 miles. Didn't hear my chirp.

At this point I am 100% positive that the noise I am having is the AFM valves. However, I am guessing that all the noises being discussed in this chain may not be the same thing.

For me:
1) Drive in manual mode (keeps engine in V8 mode) and no noise.
2) Pull fuse 32 from front (take power away from AFM valves) and no noise. Did cause check engine light, which has since turned back off after 4 starts over the past 24 hours (start after replacing fuse yesterday afternoon, 1 extra start when I got home last night, start this morning, and then light was off when I started after work today).
3) Every time I see the green V4 switch to the red V8 I get a chirp. (accept if fuse 32 is pulled and the valves are stuck open - then no noise).
4) Happens in all driving modes (Eco, Tour, Sport, Track - didn't bother trying weather)
5) Sound comes from rear of car.
6) Have driven other 2016, A8, NPP at the dealer and they don't make this noise, so it is not typical.

Dealer update:
They called this morning and said that GM Brand Customer Care (a level above the Tech Center for whatever that matters) had given them a process to follow to go thru the different valves and find out which one was making the noise. He said that they will step thru the process and then have to drive the car after each step to check the results. He said that if it helps them diagnose the issue, he imagines that the info will be spread out to other dealers.

Sounds a little worthless at this point, as I expect it will point them to the AFM valve and hopefully a 2nd exhaust replacement. Not sure why it would matter if it was one side or the other (or both). But, got to let them work the process I guess. I will let them know what everyone has shared here and what I have found. I am going to drop it off on Friday morning for them to see what they can find.

-------------------------------------
For those still trying to find out if it is the AFM valve or not, I would run thru items 1-3 that I listed above to verify if your issue is the AFM valve. If you still hear your noise when you know it isn't going between V4 and V8, then it is likely another issue and not the AFM valve.

To check the NPP valves, as other have said - you can switch between stealth and track mode from the center touch screen (home, gear symbol (options), Driving Mode, Engine Sound Management (I think car has to be running and not just accessory power on, but I could be wrong). Pick stealth (NPP closed) and drive around for a while. Then put it in track and drive around for a while. If noise is absent in one mode vs the other... that might point to NPP valves.

For other vibration type noises... may be some sort of resonance at a certain speed/rpm (I am grasping here in an attempt to help). Lots of different things to try with listening at different speeds and over different driving surfaces.

Will update Friday or Saturday. Thanks everyone for all the information and support.

seCen

If there is a problem with AFM valve, I think putting the exhaust to silence will allow you to be able to listen to the sound more clearly.

I think its the NPP baffles that causing the problem because I have the same chirp when doing the v8-v4 transition too but I can also hear it when I manually close and open the baffles/valves. Either way, shouldnt replacing the whole axle back exhaust fix either problem?

bjones7131

Thanks for the update, sounds like we r making progress. I am going to try the stealth mode.

bjones7131

If it is the AFM valves GM may have to engineer a fix for the valves before replacing. Seems like they have a design problem and all the replacement valves may have the same flaw or otherwise they will be just changing parts with no real root cause fix for the valves and hoping you get a good set without the noise. Thanks for updating.

Highplains

My "warble" or whatever it is must be different that the rest of you. I took out both my Range Technology device so it would stay in 4 cylinders and the fuse and got no change in the sound. Put the R.T. back in so it would be V8 only-no change. It always occurs at exactly 1500 RPM irregardless of the gear or mode. So until GM comes up with a fix, I'll just put up with it. No apparent harm as so far that I know of. I've never been too much more than a shade tree mechanic but it just does not sound like it would be a tranny or engine component but we'll see.

bjones7131

I am at a loss myself. I have driven in manual that is supposed to render the aft vavles open and i still get the noise. I have changed to stealth mode and still no change. I can now hear it at low speed at times driving out my driveway. I am going to take mine to a bigger dealership that deal with more vetts a see what they think. It sounds like something rubbing on the wheel at the same point as it goes around. Wierd, i hope we chase this problem down soon.

Arctic C7

Dropped car off Friday morning. They kept it over the weekend and are going to continue talking with GM support on Monday. Didn't get to talk to the tech before he left Friday, so not sure what the results of their diagnostics process were.

Not really enjoying the Malibu loaner.

Will update more next week. Although, it sounds like some of you are having different issues than I am, based on your test results.

Ed Ramberger

Does my description sound familiar to anyone here?

http://www.stingrayforums.com/forum/...-please-6.html

Strake

Yes. Warble is the best choice of words I've seen yet. I always get it at a steady cruise pace of about 1200 to 1600 rpm. Only when foot is lightly on the gas pedal. If I take my foot off and coast, noise stops. During heavy acceleration, no noise.... doesn't matter if it's in E mode, T, or S. i've also tried changing the exhaust from my usual Track, to Stealth. Still does it at STEADY cruise rpm / speed. Always seem to hear it from my left ear, coming from the back end of the car.

awright2009

I think I may have what you are talking about, sounds like an exhaust leak or an old truck kind of clicking exhaust sound, notice it at low rpm, haven't played with manual mode or fuses to see if it goes away though

bjones7131

I contacted the Customer Service guys on this forum and they took my car info and will contact my dealer for an added layer of support. The more I drive my car I think it is a bad rear end or wheele bearing. If I listen closely I can hear it easing out of my driveway at very low speed and it seems to be getting worse. It sounds like a bad bearing or something in the drive train when it is loaded (accelerate). I also contacted a bigger corvette dealership near me and they want me to bring it in to take a listen so if my orig. dealer doesn't pan out I will go this route. I hope U guys with similar issue are getting resolution. Post up your experience so we can keep this post updated and maybe some of us can find the problem and others can follow up with their dealership for a fix.

Strake

Funny you should say "Wheel Bearing"....... that was my initial thought on ours.... it even sounds like the one I had on my Buick LaCrosse (former Company Car) 2 years ago. For me, the thing that changes that thought is that it goes away as soon as I lift my foot from the gas pedal. Also, you can try driving at a steady speed, hearing the sound, and put the car into neutral..... wheel bearing sound will continue, something else will likely cause the noise to stop.

Forgot to add, I've also monitored the V4 versus, V8 mode possibility that's been discussed and it doesn't seem to matter.... does it in both AS LONG as I'm at a steady 1500 RPM or +/- 100 or so rpm.

bjones7131

I agree about wheel brng. And the way it should act. It may be rear end, ring and pinion and when you put a load on it is when the sound shows up. Mystery to me but i am set on finding the root cause. Hard to believe it could be something in the exhaust system but who knows.

Highplains

IMHO, we are dealing with two different noises here-both from the rear. The folks that are saying it sounds like a "Warble" or similar sound (including myself) seem to experience it at around 1500 RPM under any drive setting, gear or whatever. It comes and goes at about that RPM. Someone suggested a harmonic resonance and that's probably it. In mine (2016, A8) it just sounds just like that. Like sheet metal vibrating. It does not sound like a wheel bearing or diff setting. They are constant and get worse the warmer they get and the faster you go typically.

Strake

Agreed........ Hadn't thought of a harmonic resonance... Any coincidence on when our cars were built? I'm grasping for any ideas at this point. Ours was built Jan 26th 2016.... Ours has done this since mile 0040. We now have about 1850 miles on it. It has gotten no worse, or no better.