-Transmission valve body Failure, Wheel lock up, ABS Event, Loud Bang and a Flashing "D" on Driver Information Center (DIC) when Lightly or Moderately Accelerating Forcing an 8-7 or 8-6 Downshift -When all four tires lock up at a high rate of speed, this puts the driver, the passengers, and all others on the road at risk for injury or death. -Yes, the problem has been found in a document by my local dealer that this issue was added to my exact vehicle's service manual on 11/27/24. The document describes in detail the exact scenario I have been involved in multiple times. It is deemed as #21-NA-275. It locks up the tires randomly to the vehicle in mid acceleration at any speed including 80 miles per hour in one instance for me. -Yes, the dealership inspected it and found the issue to correlate with the newly added section to the service manual, 13333166. This document ID is 5925530 and the added information to the dealership is #21-NA-275. The GMC manufacturer has been contacted as of 3PM MST 3/14/25. Insurance doesn't deal with mechanical problems. The police will only be involved when there is death or injury. -No. The only warning that happens is simultaneously as the vehicle locks up the tires causing the driver (me) to inevitably try to save myself and others, swerving and trying to focus on not hurting myself or others but I did notice the "D" flash on one of these occasions. This is the most dangerous issue with a vehicle I have ever even considered. At any time, for any reason, all four tires can lock up at any rate of speed and cause multiple casualties. The way to fix this is to spend $3,000 which I am sure many people like myself do not have. This means there are thousands of these exact make and models of vehicles on the road right now. Please do not take this lightly as I have almost crashed multiple times with people in my vehicle due to no fault of my own.

- Rapid City, SD, USA

The contact owns a 2020 GMC Sierra 1500. The contact stated while accelerating from a complete stop, the vehicle lunged forward. The contact stated that the failure recurred while driving at various speeds depressing the accelerator pedal, and while decelerating to come to a complete stop. The check engine warning light was illuminated. Additionally, the contact stated that while coming to a complete stop at a traffic light, the vehicle lunged forward violently, as if the vehicle had been rear-ended. The vehicle was taken to Quality Plus Automotive, where it was diagnosed that the transmission had failed and needed to be replaced. The local dealer, Leith GMC (919) 366-1000), and other dealers were contacted and informed the contact that an estimate for the repair could not be provided because the transmission part was not available. The vehicle was repaired by Quality Plus Automotive. The manufacturer was notified of the failure and referred the contact to the NHTSA Hotline for assistance. The failure mileage was approximately 75,450.

- Wake Forest, NC, USA

Vehicle shifting poorly, and I have had a bunch of brake and rotor issues.

- Zachary, LA, USA

Lifters failed and cam shaft was busted. Standard issues with 6.2L engines. Was traveling down highway and vehicles was shaking violently. Inspection report available. Has been inspected by GM service center. No symptoms or warnings prior to failure.

- Peru, IN, USA

GM 10L80 Speed Transmission Pump Idler Gear Failure causing erratic shifting, lurching, or being stuck in gear. Dealer confirmed and recommended to replace the transmission. Transmission was replaced out of pocket in December. The issue is widespread on youtube.

- Madison, AL, USA

See attached document for complaint.

- Ekalaka, MT, USA

Motor seized at 52,000 miles.... replaced motor... at 72K miles, lifters and rods had to be replaced on the 2nd motor. Transmission also failure at 72K, being replaced.

- Jonesboro, AR, USA

The contact owns a 2020 GMC Sierra 1500. The contact stated that while accelerating from a stop light, the rear wheels seized. There were no warning lights illuminated. The vehicle was diagnosed by a mobile mechanic with transmission failure. The vehicle was towed to the residence. The dealer was informed of the failure. The contact was informed by the dealer that the repair was not covered under warranty due to the mileage. The vehicle had not been taken to the dealer. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was 82,000. The VIN was not available.

- Fort Mill, SC, USA

The truck was dropped off on November 11th of last year due to a valve body failure, and I-??ve been informed that repairs cannot be completed because the necessary parts are unavailable. I purchased the truck in late August of last year and am now stuck making payments on a vehicle I can-??t even drive. When I approached the GMC dealer about trading it in or having them buy it back, they said trading it in was an option but couldn-??t offer anywhere near what I paid. To make matters worse, they have no timeline for the repairs, and buying it back isn-??t an option.

- Knoxville, TN, USA

The contact owns a 2020 GMC Sierra 1500. The contact received notification of NHTSA Campaign Number: 24V797000 (Power Train); however, the part to do the recall repair was unavailable. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The contact stated that there was a loud clanking sound underneath the vehicle while starting the vehicle. There were no warning lights illuminated. The vehicle had been taken to the dealer and was diagnosed with transmission failure. The contact stated that the transmission had been repaired twice however, the failure persisted. The vehicle was taken to the dealer again and the transmission was replaced. The dealer was contacted about the recall and confirmed that the VIN was included in the recall however, the part to do the recall repair was not yet available. The manufacturer was not made aware of the issue. The failure mileage was 50,000. Parts distribution disconnect.

- Henderson, NV, USA

Shuttering while in motion at a speed of 35mph or above. My 2020 GMC SIERRA 1500 AT4 CarbonPro while driving at or above speeds of 35mph experiences a hesitation and severe Shuttering while trying to maintain any speed of 35mph or above. The hesitation causes extreme vibrations and hesitation when lifting or applying foot to the accelerator. This happens in any drive mode also with cruise control on or off as well as shifting into low and being in any gear trying to prevent it. It also does this on any road and condition. It feels like a slip in the transmission or torque converter, possibly could be the rear end or variable valve timing as well. And when taking of from a red-light or stop sign it slips as if the truck has lost traction, but it hasn't. This is very dangerous and could be the cause of a serious accident when trying to accelerate. If your traveling at hwy speeds it feels as if the brakes are being applied and the tires are going over a washboard which could cause a collision, tire wear, or driveline damage.

- Covington, LA, USA

DEF Emissions warning and Engine Emissions warning lights suddenly appeared. DEF Emissions warning went on and off multiple times in the two days before bringing to a GMC service location. Informed that the DEF Tank heater failed, a known problem, but that they likely would not have a repair available for over a month and would not be covered by any warranty. The vehicle is now speed limited to unsafe speeds on highways while waiting for the repair.

- Jber, AK, USA

There has been a recall on the 2020 sierra 1500 for the driveshaft which causes shuddering and vibration which my vehicle is exibiting but my vin is not on the recall list

- Miami, FL, USA

At 103,000 my 2020 AT4 5.3L V8 had a P0307 code thrown. Cylinder 7 misfire. Driving highway speeds, sudden loud pop and then the service engine light came on and automatic braking engaged, and the idle got extremely rough. Ended up being a bad lifter, bent rod, tore lobe off of the camshaft. Roughly 8,000 for the repair, new cam, new lifters, spark plugs and coil packs. Now only about 3,000 miles later, driving, sped up to pass on the interstate and another misfire, P0306 this time Cylinder 6. Same symptoms check engine light, automatic braking, rough idle. Seems to be another failed lifter and bent rod. Currently awaiting diagnostic for this second misfire issue. When speaking with the tow truck driver and the mechanic both mentioned a significant rise in cases like this. There is definitely something wrong with the design that the manufacturer needs to be help responsible for. I have less than a month ago replaced all the lifters only to have another one fail again.

- Hagerstown, MD, USA

Transmission failed at 75,000 miles, yes it is available for inspection. Truck went into limp mode on the highway and turned into a very dangerous situation, I was barely able to exit the highway. Yes the dealership Martys GMC in Kingston MA has confirmed that it is transmission failure. My vehicle has been sitting on the lot of Marty's GMC since September 13, 2024 waiting for a backordered part to fix the transmission at an estimated cost of $2,500. The warning check engine light followed by every single lamp on the dash appearing on [XXX] which is the date of transmission failure. After careful research of this issue I have found this is a widespread problem with this particular 10 speed GMC transmission in my 2020 GMC Sierra that I am still paying car payments on. I have rented a vehicle at my own cost for the past 4 plus weeks to get back and forth to work. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

- Kingston, MA, USA

The AFM/DFM system in these trucks are making the engines and transmissions go out around 70k miles. The lifters fail right around the same time factory warranty runs out then your left with a 6 thousand dollar bill to have it fixed. I hope this becomes a recall because numerous people I talk to are getting rid of they're gmcs and chevys and going elsewhere.

- Murfreesboro, TN, USA

The transmission went at 67,000 miles and posed a safety issue when my husband was driving & suddenly couldn't drive above 1st gear. Vehicle is at the GM dealer and has been for weeks, but there have been so many issues with the transmissions of this year, make & model, that the transmissions are on back order and we are told it can be MONTHS before they get one in. The dealer already has another one that has been waiting for once since April. We know of others with this same issue on this make/model/yr, as well as engine issues, but yet there are NO recalls for this issue. The only warning that came on was when the issue occurred- no prior warning or indications. GM is involved but make no comment on why there isn't a recall for an obvious known issue.

- Winterport, ME, USA

Has happened three times. 1st and 2nd time driving down road towing trailer, rear wheels locked up for 12-15-?? while driving 50-55mph. I had thought it was my trailer axel. Happened twice within 6 miles. 3rd time was 1 month later. Rear Wheels locked up driving on interstate at 70-75 mph. I estimate that i traveled 1,800 miles between the 2nd and third incident. Vehicle is at the dealership getting inspected for repairs No warning lamps before, almost every warning light came on after incident If this happened on a wet, ice, snow or dirt road this could have caused a serious accident. It would also be bad in a curve. Dealer took for road test but did not have any luck recreating the issue. They checked the differential oil And it didn't have any heavy metals. They are going to take the differential apart to inspect it to verify. They checked my battery and said it needed to be replaced. Also a wheel speed sensor needed to be replaced.

- Daphne, AL, USA

Lifters Failed in November 2023 and had repaired major engine damage including 4 cylinders, cam shaft, lifters, gaskets etc. After major repair work done. Truck is now doing same exact thing in January 2024. The dealership is stating they will not look at the vehicle unless i buy a new battery. I asked them to try a used battery to see if that makes a difference. And then if it is the battery i will replace. I was hung up on after the technician doug Pedersen stated ill have a supervisor call you back.

- Peoria, AZ, USA

The right side started clicking out of no where when I turn the steering wheel

- Southfield, MI, USA