The fricking fact a DTC tripped pointing to a possible DCT issue and the seller/dealer just ignores it ! ?
The eighth-generation (C8) Chevrolet Corvette became one of the most coveted sports cars when it went on sale in 2020. And it is a top-performing sports car the Z06 model even won Road & Track's 2023 Performance Car of the Year award
.But as the C8 left dealers' lots, online C8 Corvette communities were abuzz with owners complaining about transmission failures.
Meanwhile, despite having filed numerous Technical Service Bulletins (TSBs) and a voluntary emissions recall around these issues, GM has otherwise been publicly quiet about the problems—until now.
Federal agencies, GM, and Tremec have not made any statements as to what the cause or causes of these select transmission issues might be.
The TSBs and the voluntary emissions recall do not reference any specific driver transmission failure complaints, and R&T is not drawing any conclusions as to the source(s) of the transmission issues.
To get more clarity, however, R&T closely examined the 17 TSBs filed by GM, and spoke with eight C8 owners, Tremec, and industry experts.
The Tremec TR9080 is an eight-speed, dual-clutch transmission that is proprietary to the C8 Corvette. When it works, it really works.
But online Corvette forums (which are known to attract a vocal minority of customers with negative experiences) are flooded with owners raising questions and reporting concerns about the transmission.
The 17 GM-issued transmission TSBs currently filed with the National Highway Traffic Safety Administration (NHTSA) are specifically related to the TR9080's service procedures.
Though filed through the same federal agency, a TSB isn't a recall, which is a government-required edict for safety-related issues that legally mandate repairs.
A TSB, on the other hand, addresses an issue with a vehicle that isn't deemed a threat to consumers or public safety, and manufacturers are not required to notify purchasers of these issues.
These are issues service-department employees can often sift out after retail customers have purchased and operated a new vehicle.
Automakers issue TSBs to keep service departments and vehicle owners up to speed with recurring problems specific models may experience and recommend the appropriate repairs.
Repairs associated with TSBs are generally considered optional, with service limited to customers whose vehicles show signs of a TSB-related fault. Repair costs related to TSBs may be covered under warranty terms, but the automaker is under no obligation to do the repairs after that warranty has expired or if there is no warranty.
GM issued its first TSB related to the Tremec TR9080 in October 2020. The bulletin was filed after customers began reporting check-engine lights and messages about reduced engine power without any realized loss of performance. GM instructed its technicians that affected Corvettes required a Transmission Control Module software update, specifically in the presence of two Diagnostic Trouble Codes. This TSB was updated most recently in March 2022, adding vehicles from the 2021 and 2022 model years.
In November 2021, GM issued a TSB asking dealers to collect and return all of the DCT filters taken off of C8 Corvettes during the car's initial 7500-mile or 1 year service for analysis by GM engineers.
The automaker wished to inspect the filters after reports of clogged solenoids impacting shift quality and drivability. A second filter service is required at 22,500 miles and every multiple of that thereafter, with a fluid replacement required every 45,000 miles.
That 7500-mile service is a shocking figure in the context of other performance cars.
For reference, Porsche's PDK, among the dual-clutch transmissions longest on the market, needs a fluid service every 12 years or 120,000 miles.
In July 2022, GM issued another TSB with additional instructions for dealers as it relates to addressing TR9080 service requirements. Chevrolet dealerships have stopped tearing down TR9080s, with corporate instead asking that troublesome gearboxes be pulled and replaced entirely.
The automaker is requesting that every replaced unit be returned to its engineers for analysis, complete with the fluid inside the case. Kevin Harty of Munro & Associates, a group of automotive and industrial engineering and teardown specialists, told R&T that if they are investigating the fluid, they may be searching for a wear issue within the gearbox.
"If they're looking through fluid, they are looking for wear," said Harty. "They're looking for essentially a premature failure mode, which in something like that, if it's not a catastrophic failure per se, it might be these little, more subtle failures that are related to aggressive wear."
In early March, General Motors issued a voluntary emissions recall involving certain C8 Corvette models from the 2020 and 2021 model years. According to the document, the recall is related to the vehicles' Transmission Control Module, which may incorrectly clear the loss of Diagnostic Trouble Code communications from other control modules, stemming from a direct loss of communication.
When this takes place, the gearbox will continue operating in its default settings, without abiding by the previous DTCs or illuminating a check-engine light.
Dealers are now being tasked with reprogramming the TR9080's TCMs with an updated software set. (the whole purpose of OTA)
GM confirmed to R&T that this is the second round of communications it has sent to owners related to this emissions recall,
as the take rate on repairs did not meet the required quotas after the initial round in California.
"General Motors has decided to conduct a Voluntary Emission Recall involving certain 2020 and 2023 model year Chevrolet Corvette vehicles," the recall states
. "The Transmission Control Module (TCM), after detecting a loss of communications fault with other control modules, may incorrectly clear the loss of communications Diagnostic Trouble Codes (DTCs) when the vehicle is keyed off and, if the loss of communications fault persists, may not detect it again when the vehicle is keyed back on. If this were to happen, the transmission could operate in a default mode with no DTC set and the MIL not illuminated."
Mike Brink, the person behind the Corvette-centric Brink of Speed YouTube channel, has been very vocal about the issues he experienced with his former C8. The 2021 C8 was the fourth Corvette Brink had owned, following a line of C5, C6, and C7 Z06s. Brink managed to drive his first C8 for nearly 17,000 miles without issue before noticing some abnormal shift behaviors at low speeds.
"The easiest way for people to really understand is if they know how to drive a manual transmission," Brink told R&T. "It felt like when you start it up, the person driving the car obviously it's a computer driving it but it felt like the computer didn't know how to let the clutch out properly. And then when you're stopping, it felt like the computer didn't know how to push the clutch in. They were braking without pushing the clutch in. That's exactly what it felt like."
Tremec was unwilling to comment directly on the matter of TR9080 replacements.
