GM Launches Investigation Into C8 Corvette Transmission

General Motors filed paperwork with the National Highway Traffic Safety Administration to launch an investigation into reported problems with the eight-speed dual-clutch transmission found in the C8 Corvette Stingray.

Some C8 Corvette Stingray owners have experienced gasket failures with their vehicle’s Tremec TR-9080 transmission, resulting in leaks, while others have observed error messages telling them to put the vehicle in park and take it in for servicing. Paperwork filed previously with the NHTSA indicates some problems could be traced back to “debris on the park position sensor magnet causing an incorrect position reading to the (transmission control module).”

After widespread complaints to GM and online, the automaker decided to launch an official investigation into the matter to see what’s really going on. The automaker sent out a letter to dealerships requesting technicians remove the transmission fluid filter when a 2020 or 2021 model-year Corvette comes in for its first scheduled maintenance at 7,500 miles. Technicians are instructed to carefully remove the filter, place it into a plastic bag without letting the fluid drain out of it and mark it with the associated vehicle’s mileage and VIN. The filters will then be returned to the warranty parts center and later inspected by GM engineers.

A poster on Corvetteforum.com previously shared communication from GM that indicated the transmission pan and gasket had been redesigned at some point during the 2021 model year. The older pan design, according to the poster, was made of steel and was connected via two studs and 13 bolts, whereas the new pan is cast aluminum and features 17 bolts. The new pan also does away with two reinforcement plates used in the original design and has a new machined groove at its leading edge to help properly seat the gasket.

GM Authority will provide an update on the C8 Corvette transmission investigation once more info becomes available. As we exclusively reported earlier this month, production of the Corvette’s eight-speed transmission will begin at GM’s St. Catharines plant in Ontario in the second quarter of 2022.

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Sam McEachern: Sam loves to write and has a passion for auto racing, karting and performance driving of all types.

View Comments (73)

  • Is it me or is GM having lots of issues? This issue, the issue with lifters on V8’s. I believe they have had past transmission issues with the Colorados and Silverado 1500’s. Oh ya, can’t forget the Bolt fiasco. It’s really sad. The prices are going up and the quality is getting worst.

    • Was thinking the same thing. Easy to see why they want to convert to EV’s. It appears they have hit the glass ceiling on engineering ability to make reliable cars and trucks. With EV’s there are fewer moving parts and the margins will be much higher. Unfortunately a massive amount of good people will become unemployed.

        • My friend has a Nissan Leaf. It left him stranded at the side of the road, and now has been at the dealership for over a month while they try to figure out the problems. It sounds like , so far, they have changed out everything but the name plate.

        • My bolts have been very very reliable. For the money spent per mile driven over my ownership the vehicles have been extremely economical. The cathode strap issue on the LG batteries for allot of media, but was very very few actual incidents. I've been overall pleased and that's why I'm on my second and will most likely have a third once this one hits 100k.

      • GM hasn’t hit the glass ceiling they are just watching things much closer
        and addressing the problems. The C8 Corvette is a complicated machine
        and there is going to e bugs to work out.

        • What a horribly lame excuse. They should work the bugs out of their complicated machine before they start selling them.

    • Yes they got a bad batch of valve springs from the supplier and several of their models had a failure in the valve train. As a member of a C8 forum, there doesn't seem to be lot of leak issues, but some. And there have been reports on the forum about the transmission parking position in the . Overall the serious problems have been few. I think GM is probably trying to get ahead of the issues with this NTSB paperwork. I've had no issues with leaks or parking position on my car

    • Maybe, just maybe, it has something to do with the layoff of thousands of engineers when GM was downsizing direct labor at the beginning of the last non-COVID recession. There has to be a downside of laying off so much inside talent, and relying on suppliers to be the watchman for their own parts and sub-assemblies. That’s like believing thousands of engineers sat around and did nothing.

      • That's what happens when engineers are replaced with bean counters. One need look no further than The Boeing Co. Unfortunately, the mantra in corporate America is short term profits over long term customer satisfaction (Toyota, Honda)

      • You apparently don't know that the DCT was designed by Tremec, not by GM? So GM layoffs had nothing to do with any transmission issues. But why worry about facts when its so much easier to spread your bias. FWIW, with 5800 miles, my '21 C8 has been perfect.

        • Ah, I just turned 7,249 miles on my 2021 C8. Took the car in for the scheduled maintenance and was informed that my transmission is leaking! Now the car will be sitting at the dealers waiting at least 2 weeks for a new transmission!

          • Ugghh. Sorry to hear that. The 2-week wait is definitely frustrating, but if it were me, I'd be more annoyed at having to drop the engine out of a nearly brand new car. Hope it works out.

          • Did they give you the ETA for the new transmission? I just received confirmation that the dealer is ordering one for my C8.

          • Same here. 2021 with less than 2400 miles. Had check engine light early on that was reset by dealer with something unexplained about the transmission. 3 weeks ago another check engine light and the car has been at the dealer since. Between GM and the Dealer it’s been a real clown show. Just goes to show, regardless of how much you pay, it still a Chevy.

    • No more than normal and not the most we have seen from the manufactures.
      A lot of issues never make the news. Nothing shady going on nor are they hiding anything. Recalls go out ALL the time for components that could make the car more unsafe than this issue.
      I had a car back in 2000 with a mass recall for a steering box nut. Apparently it could back itself out resulting in the inability to turn right. Yea. I like turning right. I do it all the time.. LOL

  • GM JUNK Problems after Problems. You pay soo much for one of these Vehicles and then the problems begin.

  • NOW “gm” is opening an investigation? The dct has been out for three model years and “gm” has known about problems with the Tremec transmission from before the release of production cars. Another reason for the “official” investigation might be that the NHTSA found out due to direct customer complaints to the federal agency.

  • No leaks with my C-8 also best car I have ever owned but I walk past it for my 2019 SCS AT4 GMC Sierra most mornings.

      • I understand your thoughts, but automobiles are not designed for the second or third owner in mind. They would be completely unaffordable if they were engines for 200k miles. Everyone should understand buying a pre owned car is at their own risk. Huge aftermarket to provide extended warranty, but the cars are designed to be as flawless as possible for the original owner and warranty period.

      • I have a 08 GMC Siara . That truck has 112,000 miles on it .The only thing I’ve ever had to do to this truck is put brakes and tires and change the oil on it. I just did the first tuneup at 105,000 miles the truck still looks like brand new. Now I can say that’s the best truck I’ve ever owned. I have a 2021C83LT loaded that cost $105,000 I have had no problems yet I have a little over 12,000 miles on that car I love this car. I have always said don’t love something that can’t love you back but I do really love this car it’s great.

    • And neither has a dct so what is the moral ? That GM can’t built reliable cars then go buy yourself a Bmr or a porsche my son just got rid of his M4 htc because of all the problems he had from having to replace the whole differential (13 k’s) to paying $3500.0 for a bumper cover
      Well he went back to his Lexus
      Me I am a C8 guy waited too long and paid too much but O love it so far. ✈️

      • Interesting comment. Wife has a 2019 X4 and the pinion bearing went bad. Is covered under warranty but the service guy tells me they will have to find a differential somewhere. I asked him why they just don;t replace the bearing and he said BMW does not allow them to do that so they MUST replace the entire differential. Looked on line and those things are $4,000 for just the differential. Got to believe labor would be at least $1,000. I am on my 5th Denali XL and the last one went 180k miles with regular Maintenance and had to replace a torque converter for at 102k miles for $2,000, not bad. Love GM products but they seem to be having some problems as of late.

        • My Cadillac had a rear end go bad, and the service advisor said GM required the whole rear end be replaced as a unit. The replacement arrived in two days under warranty. Word around town is the dealerships don’t have mechanics who are proficient enough to dive into engines, transmissions and rear ends. They call them code readers. Hope that isn’t the case.

          • Unfortunately “code reading” is what the skill has become. It’s sad but a good mechanic seems to be becoming a lost art nowadays.

  • How about taking care of owners of C7s with less than 15,000 miles on them, with horrible transmissions that shutter? Out of warranty by time but not mileage. Bad business and customer service.

    • 2016 Denali 6.2 with 8 speed trans.....shutter and shake just before warranty expired....replace fluid with new moble1 II fluid
      at dealer with CORRECT amount after flushing trans 2 times...fixed it.....but why don't GM recall for the fix?
      Leaves bad feeling about trusting them.

      • I had a 2015 Denali XL and had the same problem. Ended up being the torque converter. Happened at 102k miles so had to pay $2,000 but that was the only major bill after 180k miles when. I traded it in. Not bad.


  • Opinions are that OPINIONS
    Fact I have owned 5 Suburbans, and 10 CorvettesI. Have yet to experience any real issues with any of the vehicles, yes there have been a few, but not anything that cannot be addressed and repaired. Seriously, an oil seal going bad and leaking is not a reason to condemn a vehicle or manufacturer, it is just a seal, an inner valve spring or a faulty switch. Get it fixed and move on! Why all the negativity ????? It’s not a perfect world.

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