GMC Complaints

Transmission will slam hard then truck goes into low power mode and doesn’t shift.

The contact owns a 2021 GMC Sierra 1500. The contact stated while the vehicle was parked, the contact attempted to turn off the vehicle; however, the vehicle remained running. A message was displayed to shift to park(P). The contact stated that the lights, radio, and other functions remained operational. On another occasion, the vehicle jerked, and the steering was difficult to turn. The dealer was contacted; however, the vehicle had not been taken to be diagnosed or repaired. The contact also stated that the trunk failed to fully close. The message that the trunk was open was displayed. The contact attempted to close the trunk and message on the displayed was turned off; however, the trunk remained slightly open. The vehicle was not taken to be diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 63,315.

The system that is not working properly is the transmission. It is available for inspection upon request. The safety of the vehicle, and myself, was put at risk because the transmission (once warmed up / at least 30-60 minutes of driving takes place) downshifts hard, making a clunking noise, and has at worst given the vehicle a rough nudge/jolt forward upon downshifting particularly from 2nd to 1st gear (it is a 10 speed transmission). This issue, when it occurs, will require me (the driver) to apply extra force to the brake pedal due to the rough downshift / jolt upon shift. The issue is exacerbated when quickly stopping the vehicle causing the transmission to downshift more rapidly. The vehicle's transmission flaws, of which this happens to be one of them, were being looked into at a certified repair facility (dealership). After the vehicle was in their possession 3 days, they informed me that they could not replicated or reproduce the issue. I informed and reminded the following: (1) the vehicle has to be warm and operated for I would state at least 30-60 minutes of driving before the issue arises (2) I have recorded videos of the problematic sounds of the transmission. (3) I am willing to go for a test drive to try to replicate the issue with dealership staff, but the issue is infrequent and the vehicle must be warmed-up and/or driven more than the typical "test drive" for the issue to be observed. The vehicle component has been inspected by a certified repair facility (dealership), but not directly by a manufacturer's direct representative, police, insurance representatives, or others. The transmission is also problematic in another way (rattling at low rpm's during upshift), but pertaining to safety the downshift is most concerning as described above. There were/are no warning lamps or messages. The symptoms of the problem pertaining to the transmission began occurring around 11,800-12,000 miles in my estimation.

The contact owns a 2022 GMC Sierra 1500. The contact stated while driving 50 MPH, the engine seized. The contact was able to cost the vehicle to the side of the road. There were no warning lights illuminated. The vehicle failed to restart and was towed to the local dealer, where it was diagnosed and determined that the engine needed to be replaced. The dealer informed the contact that the parts were on backorder. The vehicle was not repaired. The manufacturer was contacted, but no assistance was provided. The failure mileage was 40,000.

The contact owns a 2022 GMC Sierra 1500. The contact stated that while driving at approximately 60 MPH, the RPM decreased while the accelerator pedal was depressed, and the vehicle lost motive power. No warning light was illuminated. The contact was able to pull over to the shoulder of the road. The vehicle was towed to the residence. The vehicle was then towed to a local independent mechanic, where it was diagnosed with a frozen crankshaft and engine seizure. The vehicle was towed to a local dealer, where it was diagnosed and determined that the engine had failed due to metal shavings inside the engine. The dealer determined that the engine needed to be replaced. No further information was available. The manufacturer was made aware of the failure. The failure mileage was approximately 64,900.

This incident happened without any warning at all on [XXX]. while driving 45mph on county road, the engine seemed to not be firing on all cylinders. Loss of power was immediate. accompanied by a rhythmic nocking that was felt and heard. I pulled off and called a tow truck. The engine is a 5.3 liter v8. At Pete Moore Chevrolet they said it was a failure of the number 8 cylinder valve lifters. that all lifters need replaced along with the camshaft due to scarring. Found through research that this is a frequent problem with engines 2014-2021. See - [XXX] , et al, vs General Motors LLC. (brought by Berger Montague) filed in the US District court of Eastern Michigan. Alleging defective valve lifters causing near or catastrophic engine failure. NHTSA has 39 active cases as well. Contacted GM Customer Satisfaction Program 3/27/25. Case #[XXX]. Goal to see with their prior knowledge of this issue could they help repair or replace the engine. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The contact owns a 2021 GMC Terrain. The contact stated while driving 5 MPH, the vehicle stalled. There was no warning light illuminated. The contact stated that the failure was like GM Product Safety Recall: N222372310 (Inadequate Fuel Pump Flow). The vehicle was towed to an independent mechanic, who determined that the fuel pump had malfunctioned and damaged the camshaft. The local dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not contacted. The approximate failure mileage was 86,000.

When accelerating, the engine revved up, switched itself from drive to park, resulting in complete loss of control and the vehicle coming to a sudden stop. The car behind narrowly avoided a rear-end collision by swerving around me. The malfunction indicator light came on for the first time, and the vehicle would not switch out of park. After turning the ignition off and on again, the vehicle would switch out of park. The GMC service inspector ran diagnostics and found fault codes related to the transmission valve components that must be replaced.

The contact owns a 2023 GMC Sierra 1500. The contact stated while driving at various speeds, the vehicle experienced a loss of motive power. The contact shifted to neutral(N) and was able to restart the vehicle. Additionally, the contact stated that while driving 55 MPH and pulling an unloaded trailer, the vehicle suddenly stalled. A message advising the contact to shift to neutral(N) and to attempt to start the vehicle was displayed; however, the vehicle failed to restart as intended. The contact was still able to use the power brakes and the power steering, which allowed the contact to pull over in a safe area. The vehicle was towed to the dealer, where it was diagnosed that the presence of copper filings in the oil had caused the engine to run roughly. The dealer determined that the engine needed to be replaced; however, the part was not available. Additionally, the average waiting period for an engine was approximately 6 months. The vehicle was not repaired. The manufacturer was informed of the failure and a case was filed. The failure mileage was 33,000.

Driving my vehicle in the mountains pulling a 16000 lb 5th wheel trailer, the engine goes into Reduced Engine Power due to a Turbo Vane Position sensor / Turbo Over Boost or Under Boost fault. This has happened 4 times in the last 3 months and has nearly caused an accident following each occurrence. The vehicle is a 2016 GMC Sierra 3500HD with the 6.6L LML Duramax Diesel engine with 75000 miles. I believe the Reduced Engine Power protection is far to abrupt in the loss of Engine Power to safely move the vehicle out of the flow of traffic. During each occurrence I was in the left lane of a 2 lane expressway attempting to pass a much slower vehicle going up a 5-8% grade and was unable to complete my pass due to the loss in propulsion which nearly caused an accident.