Vibration Help
Thread Starter
Intermediate
Joined: May 2023
Posts: 28
Likes: 10
From: Dilworth MN
Vibration Help
I have had my 2015 C7 for about 3 months now (3LT coupe, A8 with around 27K miles on the clock). Over the last few weeks I have noticed that when driving on cruise control at around 70 MPH I can hear a very faint medal vibration noise that almost sounds like something hitting against a piece of sheet medal at a high rate of speed. I only ever notice it when the car is in V4 mode. If I put it in manual mode and cruise at 70MPH I don't hear the noise. When I drove it last I replicated the problem and just switched to manual mode and the sound immediately went away. It is also not consistent and the noise goes away by itself many times without changing a thing (since I typically notice it while cruising with the cruise control on).
Not sure if this is related to the A8 transmission issues I have read about? I don't notice any studder at all when going through the gears or any other problems with the transmission that I know about. I can usually feel when it goes from V4 to V8 but only if I am really paying attention.
Any help/guidance you have would be much appreciated. Since I am relatively new owner I am not sure if the triple flush was done...
Not sure if this is related to the A8 transmission issues I have read about? I don't notice any studder at all when going through the gears or any other problems with the transmission that I know about. I can usually feel when it goes from V4 to V8 but only if I am really paying attention.
Any help/guidance you have would be much appreciated. Since I am relatively new owner I am not sure if the triple flush was done...
Last edited by scottmn4; Aug 22, 2023 at 01:29 PM.
Instructor
Joined: Jul 2019
Posts: 190
Likes: 84
From: Tucson AZ
I have had my 2015 C7 for about 3 months now (3LT coupe, A8 with around 27K miles on the clock). Over the last few weeks I have noticed that when driving on cruise control at around 70 MPH I can hear a very faint medal vibration noise that almost sounds like something hitting against a piece of sheet medal at a high rate of speed. I only ever notice it when the car is in V4 mode. If I put it in manual mode and cruise at 70MPH I don't hear the noise. When I drove it last I replicated the problem and just switched to manual mode and the sound immediately went away. It is also not consistent and the noise goes away by itself many times without changing a thing (since I typically notice it while cruising with the cruise control on).
Not sure if this is related to the A8 transmission issues I have read about? I don't notice any studder at all when going through the gears or any other problems with the transmission that I know about. I can usually feel when it goes from V4 to V8 but only if I am really paying attention.
Any help/guidance you have would be much appreciated. Since I am relatively new owner I am not sure if the triple flush was done...
Not sure if this is related to the A8 transmission issues I have read about? I don't notice any studder at all when going through the gears or any other problems with the transmission that I know about. I can usually feel when it goes from V4 to V8 but only if I am really paying attention.
Any help/guidance you have would be much appreciated. Since I am relatively new owner I am not sure if the triple flush was done...
Team Owner
Joined: Jul 2004
Posts: 28,502
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From: Hartford WI
Le Mans Master
Joined: Sep 2013
Posts: 7,143
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From: Kannapolis MA.
Ever notice what RPM do you hear this?This is a reason why my C7 ever went in v4 mode.44K miles no eco.I believe it hurts the drivetrain from day 1.
This is why a Range device was created.
Back to OP question.Low RPM creates economy.Remove cylinders,more economy,more vibration.Vibration makes items loosen up. Sounds wrong doesn't it when in V4?I wouldn't know.
1st step get it on a lift.Check all you can for loose or rubbing parts that shine where rubbing.A experienced c7 teck could probably listen for 2 minutes and know what it is.My car would get the look under lift first.
This is why a Range device was created.
Back to OP question.Low RPM creates economy.Remove cylinders,more economy,more vibration.Vibration makes items loosen up. Sounds wrong doesn't it when in V4?I wouldn't know.
1st step get it on a lift.Check all you can for loose or rubbing parts that shine where rubbing.A experienced c7 teck could probably listen for 2 minutes and know what it is.My car would get the look under lift first.
Thread Starter
Intermediate
Joined: May 2023
Posts: 28
Likes: 10
From: Dilworth MN
I do not hear the noise at idle and never upon acceleration. The only time I hear it is when using cruise control and at a set speed and the car is in V4 mode. When I hear the noise and speed up just a bit it goes away. The sound is very faint.
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Joined: Jun 2001
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From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
The main test for A8 shudder is to shift from D to M when the problem is happening (70 MPH is usually the speed and V4 is usually the condition). If the problem goes away, the triple flush is usually the answer.
Elmer
Elmer
Pro
Joined: May 2022
Posts: 575
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From: Peoria, Arizona
There is an old video on youtube showing the production of the new C7. A corvette engineer literally says there is a lot of vibration/stress put on the drivetrain in V4 mode. Because of that and all the torquetube failures, I would NEVER have it in V4 mode if I were you.
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Instructor
Joined: Oct 2019
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From: Denver, CO.
I have a '14 with the A6 and have used the Range device for 4 years without incident. However, I do have to get an emissions test annually and thus must remove the device and drive in AFM mode to get the monitors reset. The AFM valves rattle, squeak and flutter during this time. I am pretty sure that is the noise you hear because how you get the noise to stop is exactly what I do as well: more gas, manual shift, etc. etc.
Team Owner
Joined: Jul 2004
Posts: 28,502
Likes: 3,302
From: Hartford WI
A dongle that does only that. Puts the car out of AFM by fooling the ECM. Now if you are out of warranty, you can program the ECM to do it and make the transmission shift firmer and better throttle tip in for a little more money.
Pro
Joined: May 2022
Posts: 575
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From: Peoria, Arizona
A range device is an electronic device you buy and connect to your car that prevents it from entering V4 mode. Many Chevy car and truck owners use them so it's nothing experimental. I don't have one because a tuner programmed the car to not enter the mode like aklim described. V4 causing failures is a well known problem in the GM world. Just do an internet search for it.
Team Owner
Joined: Jul 2004
Posts: 28,502
Likes: 3,302
From: Hartford WI
A range device is an electronic device you buy and connect to your car that prevents it from entering V4 mode. Many Chevy car and truck owners use them so it's nothing experimental. I don't have one because a tuner programmed the car to not enter the mode like aklim described. V4 causing failures is a well known problem in the GM world. Just do an internet search for it.
Thread Starter
Intermediate
Joined: May 2023
Posts: 28
Likes: 10
From: Dilworth MN
Aklim - can you share more details on the ECM program you mention?
Team Owner
Joined: Jul 2004
Posts: 28,502
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From: Hartford WI
https://www.diablewtune.com/package_deals.html#i38245
No AFM and he firmed up the shift and increased the throttle response. Cheaper than buying the Range unit and the Soler TB unless you can get one that will have a higher intake
No AFM and he firmed up the shift and increased the throttle response. Cheaper than buying the Range unit and the Soler TB unless you can get one that will have a higher intake