2026 GMC Sierra 1500 transmission problems

Filed Oct 21, 2026 · Electrical, Engine · IL

While driving the truck it randomly shuts down, message on dash says shift to park to restart. No check engine light comes on or any other message. When it does this, the truck goes into park. It has been to the dealership 3 times and has not been fixed!

Filed Oct 15, 2026 · Brakes, Engine · TX

On 10/15/2026 I was making a slow right-hand turn up a slight incline into a parking lot when the vehicle braked very hard and the transmission made a grinding noise. I looked at the dashboard, and it was showing that the truck shifted into park while I was driving. The electronic brake engaged as well. I tried putting the truck back into drive, but it would not go into drive. On the dash there was a Service Transmission warning. The push to start engine button still had the green LED on as if the vehicle was running. I pushed the start engine button and the engine started (I didn't realize until now that the engine had shut off). At this point the truck would shift into drive. Another point of note is that I had turned off the Auto Stop feature. I do this every time I start my trip. The truck will be looked at on 10/16/2026 by the dealership. I did report the problem to the service department of the dealership. This incident was the first time it ever happened and there was no warning.

Filed Oct 8, 2026 · Electrical, Engine · FL · crash

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. Requested GMC pay for damage resulting from collision, as clearly the unattended driving appeared related to gearshift control, but was refused. GMC stated that unattended driving was not possible and did not result from the detected failures.

Filed Oct 6, 2026 · Engine, Fuel system · LA

While driving on a public road, the 6.2L L87 V8 stalled without warning. There was heavy smoke and an oil trail of about 300 yards behind the truck. The engine would not restart, and the transmission would not shift into neutral. The truck was moved a short distance off the road and towed the next day to the selling GMC dealer. Odometer was 4,663 miles. Oil life remaining was 38 percent. The truck was stock, with no modifications, and was operated on premium fuel. No warning lamp was noticed before the stall. The failed engine is at the dealer and currently under inspection. The dealer inspection is not finished, and no written cause has been provided. This is a sudden loss of propulsion. Please associate this report with Engineering Analysis EA26005 concerning connecting-rod and crankshaft failures in the GM 6.2L L87 engine.

Filed Oct 2, 2026 · Engine, Transmission · TX

The powertrain/transmission is malfunctioning. The vehicle shutters, vibrates, and surges forward when coming to a stop, as if it wants to take off on its own. These symptoms began within the first couple of days after purchasing the vehicle on XXX. The valve body was replaced, but the issue continues. The vehicle is available for inspection. GM Case Number: XXX Dealership TAC Case: XXX This creates a serious safety risk. When stopping, the truck shutters and unexpectedly tries to lunge forward, which could cause a collision with another vehicle or pedestrian. The unpredictable movement makes it dangerous at intersections, stop signs, and in traffic. The dealership has reproduced the issue multiple times and performed diagnostics, but the shuttering and surging continue. The vehicle was last inspected around XXX. On XXX, I called GM to speak with [XXX] for an update on when a GM representative/technician would inspect the truck. I was told the case had been closed even though no resolution or inspection occurred, and [XXX] never called me back. No other agencies have inspected it. There were no warning lamps. Symptoms began within days of purchase and include shuttering, vibration, surging forward when stopping, and inconsistent acceleration. These symptoms occur daily and have worsened over time. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 30, 2026 · Transmission · 2,000 miles · TN

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.

Filed Sep 29, 2026 · Transmission · TX

engine stall on the highway

Filed Sep 28, 2026 · Engine, Fuel system · VA

Truck was sold to me and the dealership said the truck did not have the defect and the oil was changed to a thicker oil as a precaution. 4,000 miles later the engine failed, was diagnosed as catastrophic engine failure due to the known recall, and was replaced, new engine is now making the same rod knocking noise.

Filed Sep 23, 2026 · Engine, Transmission · TX

While turning right and at a slight incline the truck engine turned off, the transmission made a grinding noise, the truck went into neutral and the dash stayed “Press Start Button”. This is the second time this has happened within 5000 miles of the struck being purchased. Several others have reported the exact same issue on Facebook forums.

Filed Sep 19, 2026 · Transmission · TX

Very similar to the federal safety agency complaints 11752469; 11762072
; 11761966
; 11761844; 11755200 while turning left into my 6 degree inclined drive at a slow rate of speed under 5 mph, my 2026 GMC Sierra SLT X31 with 1500 miles suddenly slams into park and shuts down. "Press start" shows on display and am able to start the truck. Twice the "Service Transmission" light has displayed. I took it to the dealer after two incidents and they could not replicate. Since getting it back from the dealer, I've had six more incidents and am taking back to the dealer with more information for them. The last incident, I was prepared for it and felt the truck begin to shut down and slammed on the brake before it shut down.