199 of the
2,284 complaints filed about the GMC Sierra 2500
are about the transmission —
9% of everything owners reported.
The worst model year for it is 2024.
199
Complaints
9%
Share of all complaints
6
Crashes
2
Fires
Transmission & Drivetrain complaints by model year
While towing my fifth-wheel trailer, I was descending a hill (I had my tow/haul switch engaged) when I noticed an issue with my vehicle. Upon reaching the bottom of the hill and beginning to decelerate, when applying gas to continue up the hill the vehicle shuddered noticeably. A warning light briefly illuminated on the dashboard and then turned off shortly afterward. Although the warning light went away, the vehicle continued to exhibit a slight vibration, particularly between approximately 25 and 50 mph. I was able to drive the vehicle home safely and subsequently brought it to the dealership for inspection. The dealership performed a diagnostic scan and retrieved fault codes. Based on their findings, they have determined that the transmission requires replacement and are proceeding with that repair. They also found a different fluid in the transmission fluid, they skipped the testing and got permission to change out the transmission
NHTSA complaint #11752346 — an unverified report by a vehicle owner.
On XXX, I was towing my camper to Copper Center, Alaska from Palmer, Alaska when my truck experienced a full transmission shut down which put the truck into "Reduced Power Mode". We descending down the road right next to Victory Bible Camp (64741 Victory Rd, Sutton-Alpine, Ak 99674) when the exhaust break turned off and the truck decreased power and the Check Engine Light illuminated. The Diagnostic that was produced by OnStar revealed 3 different codes. ( P0700 TCM, P0747 Pressure Control Solenoid A is stuck in the "ON" position, C116b faulty brake pad wear sensor.) I called GMC of Palmer and GMC OnStar advisor, both informed me that the truck needed to be towed. My safety concerns is this.... I had minimum cell phone signal and not a gas station or service station within MILES. I was on the side of the Alaska Highway 1 which is a major thoroughfare for traffic going to and from [XXX]. Thankfully there were a few kind folks that pulled over to offer assistance. My truck is a 2023 GMC Sierra 2500hd with only 26,262 Miles on it. I purchased this vehicle XXX. (It Still has the Temporary Tags on it.) If had been in a different part of Alaska when this transmission failed to function properly then we could be talking about a life or death situation. Especially, if my child was with me. I was hauling my camper that weighed ATMOST, 7,000 pounds. This is less than 40% of the trucks ability. I feel that this could put someone into a dire situation had they not had the experience with emergency situations like I have had. (Prior Military Service). I have also filed a complaint with GMC Motors. Case# XXX. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
NHTSA complaint #11748895 — an unverified report by a vehicle owner.
I am reporting repeated failures involving both the transmission and diesel emissions (DEF) system on my 2021 GMC Sierra 2500HD Denali equipped with the 6.6L Duramax diesel engine and Allison 10-speed automatic transmission. While under warranty, the truck required replacement of the aftertreatment fuel injector and later the Reductant Control Module due to DEF/emissions system failures. General Motors also completed recall-related transmission software updates on the vehicle. At approximately 154,833 miles, the transmission began shifting improperly, set transmission fault codes, and required complete replacement at my expense. Less than 5,000 miles later, the vehicle again experienced a "Service DEF System" warning with multiple diagnostic trouble codes. Repairs required replacement of the DEF tank, DEF heater assembly, and NOx sensor. These repeated failures involve major drivetrain and emissions components on a heavy-duty truck. DEF system failures can place the vehicle into reduced-power (derate) mode, limiting vehicle performance and creating potential safety concerns while driving or towing. I am submitting this complaint so these failures can be documented as part of NHTSA's evaluation of similar vehicles.
NHTSA complaint #11746749 — an unverified report by a vehicle owner.
I was merging onto the highway in my 2024 GMC Sierra 2500HD AT4X equipped with the 6.6L Duramax engine at about 50mph when the gauge cluster emitted a “Reduced Acceleration Drive With Care” message followed by a check engine light. The check engine light presented indicated a “P0747” and “P0700” code. The vehicle was then stuck in 5th gear at highway speeds. Luckily there was no traffic present during this event due to the reduced acceleration of the vehicle and confusion caused to the operator. This could have been a dangerous situation due to the sudden change in handling of the vehicle. I have since then had the vehicle towed to the dealership in which it was purchased from for them to do their investigation to see how to fix the issue. This is a very well known issue with these GM heavy duty pickups. There is currently a recall on these trucks for this exact issue but my truck at this point in time is not included in said recall. I believe the recall is for 2020-2022 vehicles. Mine happens to be a 2024 which uses the same transmission as the older model vehicles in the recall. There are many other owners of these trucks like myself who have experienced this exact same issue. I’m sure this isn’t the first time this issue has been reported either. Something must be done about this.
NHTSA complaint #11742581 — an unverified report by a vehicle owner.
We keep getting an error message that shows we need to service DEF SYSTEM, it also started to limit my MPH and is now locked at 55 MPH. initial check of the DEF SYSTEM shows a malfunctioning module. it has been happening over the last year to 18 months. they would reset it or it would sometimes go away on its own after having to drive it in order for the error to clear.
NHTSA complaint #11741364 — an unverified report by a vehicle owner.
The ABS light came on while driving. Tire and components were removed to expose the axle housing. It was determined by the parts manager at DeBauche Truck and Diesel that the rear wheel hub nut had come loose and destroyed the threading. The damage was catastrophic, in that continued use of the vehicle may result in an accident and the vehicle cannot be driven until remedied. GM customer satisfaction program released a notice dated January 2018 for this specific safety issue. Reference number N172120230. A replacement axle cost was 2078.35 with additional parts and labor to be determined. Vehicle was purchased 8/29/2025 from Morrie's West Salem with no indicated reports of the issue through carfax and no related recalls through nhtsa. The vehicle had 30,967 miles at time of purchase.
NHTSA complaint #11730500 — an unverified report by a vehicle owner.
While driving on the highway at normal speed, my vehicle was operating completely normally with no warning lights, messages, or prior issues. Without any warning, the vehicle suddenly lost the ability to accelerate and felt as if it had been shifted into neutral. I immediately had to pull over to the side of the highway, as this created a dangerous situation with surrounding traffic. The vehicle had to be towed to a mechanic. Upon inspection, I was informed that a coolant line connected to the transmission had completely blew off, causing a rapid loss of transmission fluid and resulting in total transmission failure. I was told this was not due to a rusted or deteriorated clamp, but rather a sudden component failure. This vehicle has been meticulously maintained and I have owned it for less than one year. There were no prior symptoms, leaks, or warning signs leading up to this incident. This appears to be a sudden and unexpected mechanical failure, not caused by neglect or misuse. The loss of power while driving at highway speed posed a serious safety risk to myself and others on the road.
NHTSA complaint #11726714 — an unverified report by a vehicle owner.
While driving down a highway doing between 45 and 55 mph the transmission suddenly and completely faulted causing the truck to come to a complete stop. Just enough power to get to the shoulder luckily. The transmission had basically completely blown out, fluid everywhere. The insurance company did not find any comprehensive damage. The entire transmission needs to be replaced. There were no indicators showing any problems, no alerts, no warning whatsoever. Mechanics said there was a lot of metal coming out of the transmission. The truck is currently in a mechanic shop awaiting the new transmission, so at this time it is available for inspection. The safety issue here is that it happened on a busy highway, and the vehicle was no longer drivable so it needed to be towed causing more time spent on the side of the road.
NHTSA complaint #11723197 — an unverified report by a vehicle owner.
The transfer case leaked out all the fluid while driving over a period of time and damaged internal parts before the first oil change. This has happened 2 times now, and is currently leaking again with less than 10k miles.
NHTSA complaint #11721851 — an unverified report by a vehicle owner.
Was driving down the highway and was approaching a red light. As I was slowing down my transmission down shifted hard and my rear wheels briefly locked up and my truck went in to reduced power Took to dealership only to find out the valve body failed and my truck wasn't covered
NHTSA complaint #11721120 — an unverified report by a vehicle owner.
A couple times I heard loud clanking coming from rear brakes. One time in particular I was trying to stop and it felt line someone had ran into my truck but must have been the rear wheel locking up
NHTSA complaint #11718162 — an unverified report by a vehicle owner.
Driving at approximately 30-35MPH merging in traffic, the transmission shuttered and went into reduced power mode. ECM reported a 747 code and valve body failure.
NHTSA complaint #11713060 — an unverified report by a vehicle owner.
The transmission made a loud noise, resulting in a sudden decrease in speed while driving in traffic. Felt similar to being rear ended in a collision. The lights came on in my dashboard including the check engine light. Tried driving the vehicle and it would shift erraticaly rendering un-driveable. Had to be towed to my GMC dealership for service. The initial diagnosis is an issue with the "valve body". a quick search on the internet presented several other users with this issue in this model truck with this transmission. The service department also seemed to be aware of the issue. If it is so widely known, why would there not be a recall placed on these vehicles? I'm glad I had already dropped my son off at school and that I was not on a Main Street where I could safely pull over and wait for the AAA driver.
NHTSA complaint #11711040 — an unverified report by a vehicle owner.
Summary of Issue On [XXX], my family and I departed Kansas City, Missouri, for a camping trip to Great Smoky Mountains National Park (Cades Cove), Tennessee, approximately 800 miles away. We were towing a 2020 Forest River Salem FSX/RTX travel trailer, estimated at approximately 6,000 pounds loaded, using a Reese weight distribution hitch with integrated sway control. This load was well below the rated towing capacity of the vehicle. On [XXX], while driving without the trailer attached, the vehicle displayed multiple warnings including “Reduced Engine Power” and a transmission system alert. I immediately pulled over, shut the vehicle off, and restarted it. The warnings persisted. I cautiously drove approximately five miles to Twin City GMC, where the vehicle was diagnosed with a failed transmission valve body. Dealer and Manufacturer Response The service manager at Twin City GMC informed me that the required valve body was on national backorder, with multiple vehicles ahead of mine, and that wait times had reached up to three months. To confirm, I contacted Molle Chevrolet (Blue Springs, MO) and Randy Curnow GMC (Kansas City, KS). Both dealerships independently confirmed that this was a known and recurring issue, and that extended backorders for the valve body were common. I was informed that GMC could provide a daily rental allowance, but the rental vehicle would not permit towing. With my family, three dogs, and travel trailer stranded 800 miles from home, this option was not viable. As a result, I was effectively forced to trade in my truck and purchase a replacement vehicle to safely return home. Manufacturer Awareness and Complaint History GMC has demonstrated awareness of this issue through service bulletins, widespread owner reports, and media documentation addressing transmission valve body failures and parts shortages. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
NHTSA complaint #11710403 — an unverified report by a vehicle owner.
Vehicle shudders while accelerating and a constant speed from 1000-3000 rpm. Vehicle will shudder/shake for hundreds of miles at highway speed. Vehicle shakes violently going up steep grade. Vehicle shake is so consistently random it makes passengers ill. Warranty claim denied by GM after issue was recognized by technician.
NHTSA complaint #11706072 — an unverified report by a vehicle owner.
Pulling into a driveway and the truck made a loud clunk and the check engine light, traction control light, and a reduced engine power light came on and the truck came to an abrupt stop. When the gear shift was put into reverse or any forward gear the truck would rev up without touching the gas pedal. The left rear wheel locked up. After paying over $700 in tow bills to get the truck towed to our house and then to the dealer we were told that the transmission had a catastrophic internal failure. This truck only has 82,000 miles on it and is a 2021!
NHTSA complaint #11703711 — an unverified report by a vehicle owner.
Upon exiting the freeway, I pressed the gas and the vehicles rpm’s went up to 4K plus on a diesel engine, no acceleration. Thought maybe there was ice and had lost traction, tried again, same thing. Then a shudder, bang and pop. The check engine light went on and informed me of limited power and acceleration. There was no acceleration. Rpm’s would go to 2000 plus just to move. Got it to the dealership and parked it. Made a service appointment. They tried to put it into reverse and it wouldn’t move.
NHTSA complaint #11703853 — an unverified report by a vehicle owner.
The transmission is locking up, to the point it stoped pulling, it has been to several dealerships, and they can’t find any problems, put another transmission in the truck and it’s doing the same thing, the dealer ship told us there’s nothing they can do for us!
NHTSA complaint #11701819 — an unverified report by a vehicle owner.
transmission locked up 8 times from 1,050 miles to current 3,885 miles. It has happens each time around 40 mph. Each time it’s like hitting the brakes. The 8th time it locked really hard like slamming on the brakes. I’m worried with winter months what will happen on snow/ice covered roads. Called dealership and was told GM refuses to do anything until it completely fails. It seems they know what the problem is but refuse to fix till the truck stops moving during complete failure. No warning lamps and dealer ship says they can’t replicate it.
NHTSA complaint #11698271 — an unverified report by a vehicle owner.