C7 engine vibration with AFM
Intermediate
Joined: Jan 2005
Posts: 31
Likes: 0
From: Wayne IL
St. Jude Donor '05
I really want to once again thank everyone that responded to my AFM issue. It was "very" helpful to hear from other C7 owners. I ended up replacing the motor mounts with an after market from a Corvette racing shop that I deal with. We did the job in about three hours (using his equipment). The vibration is still there but it is much, much less and I am now a happy camper again. Thank you all.
Cruising
Joined: Jun 2015
Posts: 13
Likes: 3
2015 C7 Does it too
I have a 2015 automatic that does it too. Vibration in the console in V4 mode after a few minutes being in V4 mode. I researched it online and found that is has to do with the powertrain cavitating in V4 mode. My cure has been finding the right gas that smooths the engine out in V4. My worst experience with it is Sam's Club gas and my best is Exxon to the point it doesn't happen.
Burning Brakes
Joined: Feb 2010
Posts: 878
Likes: 61
From: Louisa, Ky
[QUOTE=AFVETTE;1587326780]I wonder if GM engineers will start tweaking the "parameters" of how/when the AFM is engaged and provide software updates as more and owners start providing real world feedback.
The only tweaking I've found is the Throttle Position Max reduced from 50% on '14s to 40% on '15s. I would like to see GM give the auto's the same programming as the stick shift cars. Only in Eco!
The only tweaking I've found is the Throttle Position Max reduced from 50% on '14s to 40% on '15s. I would like to see GM give the auto's the same programming as the stick shift cars. Only in Eco!
4th Gear
Joined: Jan 2018
Posts: 4
Likes: 0
Vibration 2014 AT
Just went on a 2000 mile road trip across Nevada and Arizona. In the V4 mode when under a light load going up a slight hill, felt like the car was going to vibrate apart!! When I press on accelerator enough for it to kick back into V8 it's fine. My wife thought we had a flat tire the first time it happened. Getting ready to take it to dealer to see what they have to say about it. Maybe there is some software update available. I hope!!!
Burning Brakes
Joined: Sep 2007
Posts: 1,048
Likes: 300
From: FL
Just went on a 2000 mile road trip across Nevada and Arizona. In the V4 mode when under a light load going up a slight hill, felt like the car was going to vibrate apart!! When I press on accelerator enough for it to kick back into V8 it's fine. My wife thought we had a flat tire the first time it happened. Getting ready to take it to dealer to see what they have to say about it. Maybe there is some software update available. I hope!!!
Tech Contributor
Joined: Oct 1999
Posts: 41,058
Likes: 9,822
From: Charlotte, NC (formerly Endicott, NY)
I have an M7 and my engine switches from V8 to V4 and back to V8 seamlessly. The only way I know it switches is by listening to the exhaust which is set in permanent track mode and closes in V4 mode and opens in V8 mode. I hear exhaust rumble I know I am in V8 mode if I hear silence I know I am in V4 mode.
If you are getting some sort of rough operation in V4 mode or during the switching there is something wrong and you should take the car to the dealer.
Bill
If you are getting some sort of rough operation in V4 mode or during the switching there is something wrong and you should take the car to the dealer.
Bill
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
x2
agree on normal also, if OP has built engines or knows them well it may feel worse to him than someone who isnt a wrench. It would drive me nuts, & cant be good for everything else long term. Guess epa doesnt give much choice so they added it in a "mode" they figured most enthusiasts would never use?
agree on normal also, if OP has built engines or knows them well it may feel worse to him than someone who isnt a wrench. It would drive me nuts, & cant be good for everything else long term. Guess epa doesnt give much choice so they added it in a "mode" they figured most enthusiasts would never use?
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Safety Car
Joined: May 2003
Posts: 3,535
Likes: 830
From: Brighton Mi
Old thread, but why do long tubes make it worse? I just got v4 put back in on my manual 7 after long tubes and a tune, so I'm just curious more than anything. I'm a tech nerd so I like to know how things work. I have an mgw shifter and you can see the shifter vibrate in v4 mode and can for sure hear the difference as it swaps modes.
Last edited by spinkick; Sep 26, 2018 at 01:32 PM.
2nd Gear
Joined: Oct 2021
Posts: 2
Likes: 0
From: Leland North Carolina
Afm
When my C7 enters the 4 cylinder mode the engines vibrates much more than I feel that it should. I have built quite a few engines over the years and this just doesn't seem right. The Chev dealer mechanics just tell me that it isn't that bad. My question is: does anyone else have the same problem (or perhaps it is normal)?
Melting Slicks
Joined: Feb 2018
Posts: 2,184
Likes: 1,050
From: North Texas
I just purchased a 2016 and have the same problem. When I'm at cruising speed it felt like I was running over rumble strips on and off. The owners manual says you can deactivate AFM (for auto trans) by not using the Eco mode and putting the trans in manual mode, you don't have to put it in manual until your at cruising speed,it works no vibration. From what I've read there are consequences to permanently disabling AFM, do your homework.
