2021 Chevrolet Tahoe power train problems

“Vehicle is a 2021 Chevrolet Tahoe Premier with under 50,000 miles. The vehicle experienced a sudden and complete loss of reverse gear, accompanied by violent lurching, sputtering, and dangerous hesitation/stuttering while accelerating between gears at speed. A certified dealership inspection physically diagnosed the vehicle with multiple stuck valves inside the transmission control valve body, requiring a complete valve body replacement. This exact mechanical failure completely mirrors the known safety defects outlined in GM Special Coverage Program N242454441, which details transmission pressure losses causing gear engagement conflicts and potential rear-wheel lock-up hazards. The replacement transmission component installed by the certified dealer failed catastrophically within four miles of pickup, again causing severe transmission sputtering and shifting failures that render the vehicle entirely unroadworthy and a safety hazard on public roads. The dealership has been forced to order an entirely new replacement valve body assembly under warranty due to a consecutive failure. General Motors Corporate Customer Assistance acknowledged that the vehicle is…”

“My car on the dash board said do not accelerate and was shaking and the gear would not go into reverse. When I tried the car would not move. I towed the car to local Chevy dealer and when I told them about N242454441 or related safety campaigns like N242454440 nothing came up for my VIN but was informed GM had this program specifically for my code ( check engine light on) reading P0776 and P0700. This was not covered.”

“The contact owns a 2021 Chevrolet Tahoe. The contact stated that while driving at various speeds uphill, the vehicle made a loud clunking sound while downshifting. While driving 70 MPH on one occasion, and while driving 20 MPH on another occasion, the vehicle made a loud clunking sound while downshifting and lost motive power, prompting the driver to pull over to the side of the road. The message "Reduced Acceleration - Drive with Care" was displayed, and the check engine warning light illuminated following the failure. The vehicle was restarted but the warning light remained illuminated. The vehicle was taken to a local dealer, where it was diagnosed and determined that the transmission control valve body and a separator plate or spacer needed to be replaced. The contact associated the failure with TSB: 22-NA-258; however, the VIN was not included. The vehicle was being repaired. The manufacturer was notified of the failure by phone and offered partial financial assistance. The failure mileage was approximately 76,000.”

“On September 19, 2026, while traveling approximately 30 mph, the vehicle experienced a sudden, hard shift. The check-engine light then illuminated. I pulled over as soon as it was safe to do so. After stopping, the vehicle would not shift into reverse and entered limp mode. The transmission malfunction created a safety risk because the vehicle’s operation and available gears became restricted unexpectedly while it was being driven. The loss of reverse also prevented the vehicle from being maneuvered normally. The vehicle was not driven after the incident and was towed from the location. The vehicle and affected components are available for inspection upon request. At this time, the vehicle is awaiting inspection and diagnosis to determine the exact cause of the transmission malfunction.”

“My vehicle had a pop and loss of power on the highway. After pulling over, I did not have a check engine light but did connect my code reader and found a P308. I felt unsafe to drive so I had it towed to a shop. I later found out the DOD system or lifter on valve #8 has failed and needs replacement. Factory recommends oil change at every 7k miles, I did them at 4K. My oil pressure was up to par with the small window of real time allowable oil pressure. The design was great on paper but one of the worst engines GM has ever made. I sincerely hope there is enough people complaining about these 2021 GM 6.2 & 5.3 engines!!”

“Our Tahoe keeps burning through oil. about 2/3 of the way through an oil changes i have to add 2 more quarts to get to the next oil change. Our tahoe was not part of the initial recall i am not sure why.”