Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2026 GMC Sierra 1500 owners, lightly cleaned up (personal details are redacted by NHTSA).
5/08/2026: I stopped outside my garage. I then placed the truck in park and exited the vehicle while running. I went inside my garage and several minutes later, heard a crash. The truck had driven forward while unattended, and crashed into the corner of my garage, causing damage to both the building and the truck. Truck indicated it was still in park upon reentry. 5/11/2026 In a separate incident 3 days later, while driving at approximately 50mph, truck engaged in an automatic braking event with no discernible cause. Simply applied what felt like 100% braking for a split second, then released. 5/12/2026: Truck taken to GMC for investigation. No codes in any modules detected. 9/20/2026: Vehicle reports transmission fault, states it should not be driven. 9/21/2026: Towed to GMC dealer. Found codes P17A8 and P189D and diagnostic code 6906361, internal fault within gearshift control module. …
The contact owns a 2026 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the transmission independently shifted to park or neutral. The contact stated that the failure had occurred while driving at slow speeds. The contact stated that during one failure, the brakes independently activated, and the vehicle shut off. The contact stated that while attempting to restart the vehicle, the vehicle started. The contact stated that the failure was persistent. The dealer was made aware of the failure by phone. The vehicle was taken to the dealer; however, the diagnostic result was not provided. The failure mileage was approximately 500.
The contact owns a 2026 GMC Sierra 1500. The contact stated that while slowly driving up a slightly inclined drive port and making a left turn, the vehicle shut off and the parking brake was activated or the vehicle suddenly decelerated. The contact stated that the failure had occurred on several occasions with three separate identical vehicles, including the loaner vehicle provided by the dealer. During the failure, the messages "Press Start" and "Service Transmission" were displayed. The vehicle was taken to the local dealer who was unable to determine the cause of the failure. The manufacturer was notified of the failure. The failure mileage was 29.
The contact owns a 2026 GMC Sierra 1500. The contact stated that while her husband was driving approximately 10 MPH, the vehicle unexpectedly shut off and independently shifted into park(P). The contact stated that previously, while the vehicle was idling in a parking lot, with air conditioner activated, the Auto START/STOP feature engaged, and the vehicle shut off. The message "Service Transmission" was displayed. The vehicle was taken to a local dealer and was diagnosed with transmission failure. The vehicle was not repaired. The manufacturer was not contacted. The failure mileage was approximately 2,000.
The contact owns a 2026 GMC Sierra 1500. The contact stated that while hauling a trailer and making a left turn at 5 MPH, at a busy intersection, the message "Shift to Park" displayed, and the vehicle lost motive power. The vehicle was restarted. The contact stated that the failure was persistent. The local dealer was notified of the failure by phone. The vehicle was taken to the dealer, where it was diagnosed that the telematics module had failed and needed to be replaced. The vehicle was repaired. The failure mileage was approximately 3,900.
The contact owns a 2026 GMC Sierra 1500. The contact stated that while driving 5 MPH, the vehicle independently shifted into park(P). The check transmission warning light was briefly illuminated. The failure was a recurring failure. The dealer was contacted. The manufacturer was contacted by phone and made aware of the failure. The failure mileage was approximately 2,000.
While driving at approximately 60 mph on an open road with no obstacles present and no braking input, the rear wheels spontaneously locked up without warning. No brake pedal input. No warning light prior to the event. No obstruction in the road. The vehicle has been subject to an active manufacturer recall for rear wheel lockup due to transmission control valve failure. The dealer's own diagnostic system generated a report showing six active fault codes in the following days including lost communication with the Brake System Control Module and Transmission Control Module. These codes were not addressed on the repair order. The dealer attributed the lockup to an Automatic Emergency Braking activation without diagnostic confirmation and performed no repair. …
I bought the truck brand new from Gregg Young in Atlantic, IA. While an hour into the drive home, the truck began shuttering as if the transmission was having problems finding the gear. I immediately made an appt with their parent dealership of Gregg Young in Plattsmouth, NE. They had the truck for a week and couldn't duplicate the transmission issues after I reported several occurrences and symptoms, they also didn't provide a service invoice of the work performed while I found was unusual. As I was driving the truck home from repairs it started hesitating and having difficulty finding gears. I didn't think much of it since the dealer claimed there was nothing wrong. This past weekend while going 65 mph down the freeway the transmission started shuttering as well as the truck and the tires began to lock up to the point of almost losing control, there was also metal on metal noises. …
I am submitting this complaint regarding a recurring transmission issue in my vehicle. The transmission consistently jerks and shifts erratically, particularly in the morning during initial operation when at cruising speeds of about 50-75 mph. This behavior occurs when the transmission temperature is below approximately 100 F and happens on a daily basis. The gear changes feel harsh and abrupt, kind of like it doesn't know what gear to be in its raising concerns about both drivability and long-term transmission reliability. I brought the vehicle to an authorized dealership for inspection. After evaluating the issue, the dealer informed me that the behavior was due to the vehicle being in "Sport Mode." However, this explanation does not resolve the concern, as the severity and consistency of the jerking appear abnormal and occur regularly under the same temperature conditions. …
I heard a loud metallic knock that was not consistent with normal engine noise. I noticed the oil pressure was on the lower end of the scale but not abnormal based on how it is displayed. I decided to take the vehicle to the dealer ASAP for an oil change (that was coming due) and discuss with them. I drove roughly 20 miles from start of noise until delivery at the dealer. The truck gave me a "Reduced Acceleration, drive with caution" message 10 miles prior to the dealership but no associated lights, engine codes, check engine light or associated alerts on the myGMC app. Dealership found oil pressure ranging between 4-8 psi, and a failed oil pressure control solenoid, heavy metal debris in the oil pan including parts of the thrust bearing and oil squirter. Entire engine and turbo replacement was required. Truck had 143 hours on the engine and 6,300 miles. …
Related recalls
Power train › Transfer case (4-wheel drive)
General Motors, LLC (GM) is recalling certain 2026 Cadillac Escalade and Escalade ESV, Chevrolet Silverado 1500, Suburban, and Tahoe, and GMC Sierra 1500, Yukon, and Yukon XL vehicles with four-wheel (4WD) or all-wheel drive (AWD), and certain 2015-2020 Suburban, Escalade, Escalade ESV, Yukon, Yukon XL, and Tahoe vehicles.
Remedy: Owners are advised not to drive their vehicle until the remedy is completed. Dealers will inspect and, if necessary, replace the transfer case assembly, free of charge.
Transmission complaints in other Sierra 1500 years
Frequently asked questions
How common are transmission problems on the 2026 GMC Sierra 1500?
NHTSA has 34 complaints about the transmission & drivetrain of the 2026 GMC Sierra 1500, 24% of the model year's 143 complaints.
Is there a recall for 2026 GMC Sierra 1500 transmission problems?
Yes — NHTSA recall 26V-289 (transfer case (4-wheel drive), May 7, 2026). Recall repairs are free at authorized dealers.
At what mileage do 2026 GMC Sierra 1500 transmission problems start?
Half of the complaints with a recorded mileage happened before about 2,000 miles, and 100% before 25,000 miles.
Is it dangerous?
Owners linked 1 crash, 0 fires and 0 injuries to transmission & drivetrain problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.