2023 GMC Sierra 1500 transmission problems

Filed Nov 4, 2026 · Transmission · 79,000 miles · NE

The contact owns a 2023 GMC Sierra 1500. The contact stated that while performing an oil change at the residence, the contact became aware that the transmission cooling system was inoperable and that the transmission cooler lines were leaking. The vehicle was taken to the dealer, where it was diagnosed and determined that the cooler bypass valve and seal had failed and needed to be replaced. The vehicle was not repaired. The contact stated that the vehicle was scheduled to be repaired at a service center. The failure mileage was approximately 79,000.

Filed Oct 31, 2026 · Transmission · WI

The shifter shorted out. This gave me one message, Service transmission right away. I drove 10miles home & scheduled service right away. The next day I started truck up and it said unable to shift soon. This is a wide known problem with the GMC Sierra. How many people have to sit on the side of the road with this known defect.

Filed Oct 27, 2026 · Engine, Fuel system · FL

On XXX, at approximately 2:30am, about 30 hours after purchase, a 2023 GMC Sierra Denali Ultimate suffered catastrophic engine failure in [XXX] during a planned 20 hour trip. The vehicle had about 49,007 miles at purchase and 49,411 miles at the time of failure. The check engine light appeared during the trip. Over five hours into the journey, shortly after passing through a one-lane construction zone with no shoulder, the truck made noises, then lost driving power and began slowing among highway traffic. The dashboard displayed "LOW OIL PRESSURE STOP ENGINE," code P0016, and a transmission warning. I had to move into another lane to reach the shoulder. The sudden loss of propulsion at 2:30am created a serious crash risk because the truck could have been struck by nearby traffic or become disabled on the one-lane road without a shoulder. The engine had received the GM L87 recall remedy on XXX involving a change to 0W-40 oil. Despite this remedy, the engine failed while the vehicle was moving. The repair order lists replacements for the engine, radiator, oil cooler lines, intake manifold and gaskets, spark plugs and wires, water pump gaskets, high pressure fuel lines, fuel pump gasket, and battery. The GMC app currently lists a "Required Product Emission Recall" for the fuel pump power control module and states that module failure can interrupt fuel flow to the engine. However, the federal safety agency VIN lookup, refreshed XXX reports zero unrepaired recalls. The reason for this discrepancy is unknown, as is whether the fuel pump recall condition contributed to the incident. I am reporting this sudden loss of driving power and engine failure despite the prior L87 recall remedy because these conditions may pose a serious safety risk. Provide Your INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 10, 2026 · Transmission · TX

Truck rear wheels locked up while going between 45 - 50 mph nearly causing accident. Driver behind me had to lock-up their breaks to avoid collision. This is happening every time I drive the truck for more than 30 minutes. It is happening multiple times a day now. I cannot drive truck - too unsafe to drive. Tried getting serviced, but local GMC dealer said they are backed up with truck transmission issues and can't get mine in until Sep 15 - 3 weeks after first reporting. No warning signs. The locking of rear wheels takes me by surprise.

Filed Sep 10, 2026 · Acceleration, Transmission · CO

Purchased above listed vehicle new in XXX. Immediately noticed a 'coolant' smell in cab. brought vehicle in for coolant smell issue on XXX and XXX. We were told that there was no issue until finally on XXX we were told the radiator needed to be replaced at OUR expense. XXX we received a letter from GMC advising the "engine coolant control valve" may fail. In XXX while driving on mountain roads (we live in [XXX]) the check engine light came on and while at 50 mph, the vehicle went into "limp mode" we lost power and speed was immediately reduced. We now know that a symptom of that valve failure is coolant smell in the cab of the car, a problem we had attempted to address with GMC from the beginning. We could have had a serious accident driving on a busy mountain road when this failure occurred. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 2, 2026 · Engine, Transmission · PA

I am reporting a serious safety concern involving a 2023 GMC Sierra 1500 Denali, 6.2L L87 V8, VIN [XXX]. This vehicle has now experienced two catastrophic powertrain failures at very low mileage. The first catastrophic engine failure occurred at approximately 23,696 miles. The vehicle was taken to a GMC dealer, where the repair documentation states that the engine had suffered significant internal damage, including damage to the #3 connecting rod, a missing connecting-rod bearing, bearing material throughout the engine, and a scored crankshaft. The dealer determined that the engine was seized and required replacement. GM replaced the engine under warranty with GM engine assembly part number 12740076. The vehicle has now experienced a second catastrophic failure. On [XXX], while traveling approximately 40 mph, experienced grinding, lurching, and knocking, followed by a complete loss of propulsion. The truck would no longer move and had to be towed to a GMC dealer. At the time of the incident, no warning lights or warning messages were observed. The transmission is also suspected to have failed, although the exact cause and extent of the transmission failure have not yet been determined by the dealer. I understand that the federal safety agency is currently investigating failures involving GM 6.2L L87 engines, including failures occurring after previous recall remedies and engine replacements. I am therefore requesting that this incident be included in the federal safety agency’s investigation and considered when evaluating the effectiveness of the existing recall remedy and the safety of replacement L87 engines. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 1, 2026 · Engine, Fuel system · CA

I am reaching out to the federal safety agency due to a vehicle that I believe will get me and/or my family in a major accident and cause serious injury or death. The vehicle that I had purchased in 07/08/2025 had a clean history report and was bought at 54,587 miles. It started having issues 8,563 miles later (odometer reading 63,150 ) on a trip that was 400 miles round trip. I was driving the vehicle on a highway at 65 mph and i felt a knocking vibration in the pedal it was not long before i could even pull over when the engine throttle had completely lost power causing the vehicle to almost come to a complete stop immediately having to steer onto the shoulder. after failing with no check engine light or warning present during the use of the vehicle on the road. it was giving off high temp/engine overheating with the engine making a continuous knocking sound in the engine. It eventually seized to work completely not being able to shift into neutral to push, and had to get it towed to the dealership 204 miles away. GM had advised the dealership to replace the whole engine which they did, and that second engine had given out 678 miles later (odometer reading 63,828.) I am now on my THIRD engine and i cannot trust or rely this vehicle for saftey or transporation. i have reached out to GM to file a claim and attempt to adress this issue to try and come to a resolution, however they denied my claim and have said that i am not "eligible" for a buyback program. I am considering getting legal attorney this is very frustrating to say the least GM is a terrible manufacturer for this issue

Filed Sep 1, 2026 · Transmission · TX

While driving truck jolts (rear wheels lock up) then downshifts into a lower gear. Appears to be similar issue as described in Recall 24V797 and 25V148. Not sure why my VIN does not show up on recall. Based on description it is the same problem. Feels unsafe to drive.

Filed Aug 30, 2026 · Engine, Transmission · OH

My wife and I were driving on the highway going slightly uphill. I pushed the pedal a bit because the power wasn't keeping speed. It continues to not maintain so pushed throttle further and the truck stalled. We traversed 3 lanes to get to the shoulder. When I stoped I tried to restart but the car wouldn't turn over but all electrical were working. We were on the shoulder for over and hour on a main highway. We had aaa tow it to the dealership where they confirmed the engine was seized and will be ordering parts. The car is still available upon request. Our safety was at risk from loosing power on the interstate and sitting on the shoulder is very dangerous. I didn't receive any warning lights prior to this occuring. The truck did undergo the peko test and passed and added new oil viscosity. It had roughly 55k miles on it. Always changed the oil before it hit 0% oil life as told by dealerships.

Filed Aug 28, 2026 · Engine, Transmission · SC

Truck went into limo mode while driving and required valve in transmission to be replaced. Went from driving normal speed to only being able to go about 15 miles and hour. Was repaired got the truck back and the next day was on the interstate in the fast lane and the truck again had speed issue reduced speed and had to coast off interstate. This time entire valve body had to be replaced. Have gotten truck back and still have hard shifting in the transmission at times. Engine was checked for recall and now I have to pay a much higher oil change price due to a GM issue. This was not a known cost when purchasing this truck.