C7 8 speed auto box issues
- Thread starter BruceP
- Start date
Invetterate
CCCUK Member
HI Bruce,
There are plenty of UK suppliers for the ATF. Here is one:
Would recommend Rock Auto for parts. See the following link :
Their site includes shipping and duty so very easy. It is likely that you will get your parts within a few days too. Even allowing for shipping and tax, oil and air filters were about half the price I could get them for over here. Anyway, see what you think.
There are plenty of UK suppliers for the ATF. Here is one:
Would recommend Rock Auto for parts. See the following link :
2017 CHEVROLET CORVETTE 6.2L V8 Filter | Shop Now at RockAuto
Transmission-Automatic Parts and More for Your 2017 CHEVROLET CORVETTE at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.
www.rockauto.com
Their site includes shipping and duty so very easy. It is likely that you will get your parts within a few days too. Even allowing for shipping and tax, oil and air filters were about half the price I could get them for over here. Anyway, see what you think.
Chevrolet
CCCUK Member
Preventative maintenance rather then experiencing any transmission "shudder" hopefully?
Roscobbc
Moderator
If you carefully 'drill-down' in to the buyers guides and on-line/USA forums relating to specific years of C8's and the potential issues that can arise for each model year........you might be tempted to avoid buying one at all......such is the minefield of rather expensive and complicated year specific things to check-out. And what if all the 'year specifics' occur at once?
I know the 'triple flush thing' is well documented......but still a crazy, expensive way of using-up costly lubricants.
I know the 'triple flush thing' is well documented......but still a crazy, expensive way of using-up costly lubricants.
teamzr1
Supporting vendor
Have you read this ?
GM Finally gets Class action Lawsuit for Crappy C7 auto Trannys
C7 Corvettes are among the half-million vehicles targeted by a class action lawsuit against General Motors just approved by a federal court. For years, some GM owners have complained about shuddering and shaking in higher gears and lurching in lower gears when shifting their eight-speed 8L45...
www.corvetteclub.org.uk
The real issue is that damn AFM, going in and out of the 4/8 cylinder mode has a bad effect on the A8 and its torque converter
Most C7 owners, when I am custom tuning the PCM and TCM controllers,
request me to turn AFM off, which prevents the ill effects and damage due to AFM
Chevrolet
CCCUK Member
Sorry Ross above, can't totally agree with the above. I know of 6 guys, including me, who have or had UK spec C7s (4 Autos/2 manuals). None of them has had any problems with them, including auto transmissions. I regard a C7 as a "bullet proof" built/reliability car, like my C6 and C4 before that were. First owners on the two manuals were Aston Martin and McLaren. Obviously bought them to find out how to build a good sports car? Been a lot of talk on here about transmission problems/"shudder" on the 8 speed autos in the US, but can't remember anyone on here saying they have experienced the problem?
teamzr1
Supporting vendor
More :
Just when things seemed to be on the up and up for the Corvette, an older issue is coming back to strike. Allegedly, GM models from 2015 to 2019 ( like C7) have transmission problems that make the trucks dangerous to drive and never received an effective solution.
We’ve been following and reporting on the C7 Corvette for having transmission problems for months, but the issue is larger than expected. It includes multiple General Motors vehicles equipped with possibly faulty eight-speed automatic transmissions.
Specifically, the units involve the General Motors 8L90 and 8L45 eight-speed automatic transmissions built between 2015 and March 1, 2019. Both units have a lot in common, but the 8L45 is a lighter unit used in fewer options.
The more robust 8L90 is more popular, and both are designed for front, rear, and AWD applications.
The lawsuit alleges erratic transmission behavior makes vehicles unsafe to drive.
A judge granted class-action status to the lawsuit, representing 39 plaintiffs across 26 states.
Drivers of the Chevy Silverado and other GM vehicles report transmission hesitation, shaking, shuddering, clunking, and hard shifts upon changing gears.
Vehicle models in the lawsuit include:
• 2015 – 2019 Chevy Silverado 1500
• 2017 – 2019 Chevy Colorado
• 2015 – 2019 Chevy Corvette
• 2016 – 2019 Chevy Camero
• 2015 – 2019 Cadillac Escalade and Cadillac ESV
• 2016 – 2019 Cadillac ATS, ATS-V, CTS, CT6, and CTS-V
• 2015 – 2019 GMC Sierra, Yukon, Yukon XL, and Yukon Denali XL
• 2017 – 2019 GMC Canyon
• Reportedly, General Motors didn’t do enough to solve the transmission problems found in Chevy Silverado models and other vehicles.
Claims report that General Motors has released 13 different technical service bulletins related to the issue shifting issue alone since 2015.
• So, technicians had 13 different things to try. Some of the bulletins recommended changing the transmission fluid, replacing the torque converter, providing a software update, removing the transmission pan, replacing the transmission cooler bypass valve (TBV), and more.
•
• But older technical service bulletins from 2017 and earlier report that the cause of the transmission problems is unknown and that General Motors was working on finding the cause and providing a solution.
• Cohen Milstein partner, Ted Leopold, is the court-appointed lead counsel on the case and shared that General Motors knowingly sold over 800,000 vehicles equipped with faulty eight-speed automatic transmission units despite being aware of the defects.
• The business decision to not tell customers before their purchase was made. Allegedly, dealers were instructed to tell customers that the hard shifts were normal and characteristic. Ted shared that this decision-making is highly irresponsible and emblematic of that General Motors believes it can get away with.
•
• Did the A8 transmission problems ever get corrected?
•
• The GM vehicles didn’t exactly receive a fix for the transmission problems. But it gets a new eight-speed automatic transmission when it was redesigned for 2019. In 2023, GM started replacing the transmission control module and reprogramming the software.
•
• There hasn’t been any clear indication if this fixed the problem. Also, if you had a 2015 model with issues, then waiting until 2023 for a potential fix is a long time.
• There was a recall related to a driveshaft issue in 2020 that could send vibrations through the transmission as well.
Just when things seemed to be on the up and up for the Corvette, an older issue is coming back to strike. Allegedly, GM models from 2015 to 2019 ( like C7) have transmission problems that make the trucks dangerous to drive and never received an effective solution.
We’ve been following and reporting on the C7 Corvette for having transmission problems for months, but the issue is larger than expected. It includes multiple General Motors vehicles equipped with possibly faulty eight-speed automatic transmissions.
Specifically, the units involve the General Motors 8L90 and 8L45 eight-speed automatic transmissions built between 2015 and March 1, 2019. Both units have a lot in common, but the 8L45 is a lighter unit used in fewer options.
The more robust 8L90 is more popular, and both are designed for front, rear, and AWD applications.
The lawsuit alleges erratic transmission behavior makes vehicles unsafe to drive.
A judge granted class-action status to the lawsuit, representing 39 plaintiffs across 26 states.
Drivers of the Chevy Silverado and other GM vehicles report transmission hesitation, shaking, shuddering, clunking, and hard shifts upon changing gears.
Vehicle models in the lawsuit include:
• 2015 – 2019 Chevy Silverado 1500
• 2017 – 2019 Chevy Colorado
• 2015 – 2019 Chevy Corvette
• 2016 – 2019 Chevy Camero
• 2015 – 2019 Cadillac Escalade and Cadillac ESV
• 2016 – 2019 Cadillac ATS, ATS-V, CTS, CT6, and CTS-V
• 2015 – 2019 GMC Sierra, Yukon, Yukon XL, and Yukon Denali XL
• 2017 – 2019 GMC Canyon
• Reportedly, General Motors didn’t do enough to solve the transmission problems found in Chevy Silverado models and other vehicles.
Claims report that General Motors has released 13 different technical service bulletins related to the issue shifting issue alone since 2015.
• So, technicians had 13 different things to try. Some of the bulletins recommended changing the transmission fluid, replacing the torque converter, providing a software update, removing the transmission pan, replacing the transmission cooler bypass valve (TBV), and more.
•
• But older technical service bulletins from 2017 and earlier report that the cause of the transmission problems is unknown and that General Motors was working on finding the cause and providing a solution.
• Cohen Milstein partner, Ted Leopold, is the court-appointed lead counsel on the case and shared that General Motors knowingly sold over 800,000 vehicles equipped with faulty eight-speed automatic transmission units despite being aware of the defects.
• The business decision to not tell customers before their purchase was made. Allegedly, dealers were instructed to tell customers that the hard shifts were normal and characteristic. Ted shared that this decision-making is highly irresponsible and emblematic of that General Motors believes it can get away with.
•
• Did the A8 transmission problems ever get corrected?
•
• The GM vehicles didn’t exactly receive a fix for the transmission problems. But it gets a new eight-speed automatic transmission when it was redesigned for 2019. In 2023, GM started replacing the transmission control module and reprogramming the software.
•
• There hasn’t been any clear indication if this fixed the problem. Also, if you had a 2015 model with issues, then waiting until 2023 for a potential fix is a long time.
• There was a recall related to a driveshaft issue in 2020 that could send vibrations through the transmission as well.
Chevrolet
CCCUK Member
As noted elsewhere, UK spec cars (autos & manuals) only go into AFM V4 when the car is in Eco mode.
Last edited:
teamzr1
Supporting vendor
A sample of only 6 C7s with the A8 in the UK is nowhere the amount of same C7s volume in the USA
Damage to the A8 is reduced with how the owner drivers the C7 and if they always set for sport mode to limit effects from AFM
Consider the load changes back/forth when AFM comes on and off to the driveshaft to A8
teamzr1
Supporting vendor
Consider how many C7 owners set to Eco for fuel mileage or the TCM defaulting to that mode, over those who set default to sports mode only
In any case there are at least 3 class action lawsuits against GM as to A8 issues which says it is not rare for at the leas shutter
when AFM kicks 4/8 cylinders on/off
Federal recalls do not happen if there was small amount of a8 issues the feds thinks is a safety issue
How many C7s in the UK that were bought used that came to the UK with the American C7 AFM setups
rather than the new ones set AFM modes for outside the USA ?
Roscobbc
Moderator
Can't say I disagree with your comments......it's just that the experiences in the 'states' seem to have been extremely high.
I do find it odd that we don't seem to hear of the transmission issues here in the UK.
Perhaps Jon's reckoning that the UK (perhaps even Europe) doesn't have enough cars to 'log' multiple issues is correct.......but the fact that the cylinder defeat only operates here in Eco mode has some logic.....and guessing that UK/EU users when setting ECO on a longer distance cruise are unlikely to rag the nuts off the car when in ECO mode......but what of personal import C7's......there must be about a 50/50 mix by now in the UK?
They still don't seem to flag-up issues like one might expect.
Perhaps the answer is as simple as that most import C7's are either early 7 speed manuals and early 6 speed autos?
teamzr1
Supporting vendor
I would assume due to the UKs weather and people driving shorter yearly mileage as we do in the USA
and the low sample counts of just C7s with A8s in the UK would see far less A8 issues
Back to the OP, as to more frequent A8 flushes that GM steers owners to is for both engine oil and A8 fluids
is the DOD/AFM/DFM, as to the A8 is commanding AFM on and off causes more internal wear to the internals
causing shedding of like clutches, gears, etc thus that crap in the fluid gets gummed up in like the solenoids causing most of the problems
So instead of GM fixing problems AFM causes to engines and A8 is to con owners to pay the price by more flushes and it costs to
keep the fluid cleaner to reduce the chances of engine or tranny issues
'd say at least 90% of my tuning customers want me to turn off AFM via the tuning and I know many GM owners, from SUV, cars, etc
that had so much damage going back to the late 1990s that they dumped even their Corvettes and swore never to buy another GM vehicle
If you think DOD of AFM is bad, the newer GM vehicles that now have DFM can now shut all but one cylinder off
For sole purpose of the demand of the feds as to fuel mileage as their way to force people buying instead EVs
and nameplates doing these designs to make national fuel mileage laws
and the low sample counts of just C7s with A8s in the UK would see far less A8 issues
Back to the OP, as to more frequent A8 flushes that GM steers owners to is for both engine oil and A8 fluids
is the DOD/AFM/DFM, as to the A8 is commanding AFM on and off causes more internal wear to the internals
causing shedding of like clutches, gears, etc thus that crap in the fluid gets gummed up in like the solenoids causing most of the problems
So instead of GM fixing problems AFM causes to engines and A8 is to con owners to pay the price by more flushes and it costs to
keep the fluid cleaner to reduce the chances of engine or tranny issues
'd say at least 90% of my tuning customers want me to turn off AFM via the tuning and I know many GM owners, from SUV, cars, etc
that had so much damage going back to the late 1990s that they dumped even their Corvettes and swore never to buy another GM vehicle
If you think DOD of AFM is bad, the newer GM vehicles that now have DFM can now shut all but one cylinder off
For sole purpose of the demand of the feds as to fuel mileage as their way to force people buying instead EVs
and nameplates doing these designs to make national fuel mileage laws