Power Train Problems of GMC Sierra 2500 - part 1

Transmission shifting - faulty shifting between 25 - 55 mph. Took truck to dealership and they state that the radiator leaked coolant into the transmission. They are replacing the transmission and radiator under warranty. Truck only has 21k miles on it. Mostly all highway.

See all problems of the 2024 GMC Sierra 2500 🔎.

Bought a 2023 GMC Sierra 2500 duramax. Went into limp mode took it to dealership the transmission was bad so they replace transmission after 3 month of dealer having my truck . Got the truck back still having issues with transmission not shifting right and the rear tires locking up at highway speeds .

See all problems of the 2023 GMC Sierra 2500 🔎.

The transmission control mod is bad. This is a persistent problem and that's why it is on back order for up to a year. It is unethical to not issue a recall as customers have to continue to pay for the vehicle while not getting a replacement of equal capabilities. I bought a 3/4 ton truck to haul for work, not getting something that can do the same while a pay $1000+ a month is wrong. For the NHTSA not to get involved, issue some sort of recall, and allow gm to continue to take people's money while their vehicles depreciate is wrong. Is this so the government can get paid back from gm for the bailout 15 years ago?.

The contact owns a 2023 GMC Sierra 2500. The contact stated that while driving approximately 35 mph, the vehicle went into limp mode, and the message "service transmission" was displayed. The vehicle was taken to the dealer, where it was diagnosed that the transmission valve body rod had failed. The valve body rod was replaced. It was unknown whether the vehicle was repaired. The vehicle remained at the dealer. The manufacturer was not notified of the failure. The failure mileage was approximately 44,546.

I am receiving a "shift to park" warning intermittently when parking my truck. The truck is in park, but the transmission does not recognize this and flashes the warning on the dash and chimes. While this is happening, I cannot lock the vehicle, and the battery is being drained. I have read that this is a known issue with other GMC models as well. I just was given a $1074 bill to replace the transmission control with park sensor.

See all problems of the 2022 GMC Sierra 2500 🔎.

Valve body went out and no eta when its supposed to get in the dealership.

The contact owns a 2020 GMC Sierra 2500. The contact stated that while driving approximately 70-80 mph, the transmission downshifted, and the rear wheels locked up. The contact was able to coast to the side of the road. The contact was unsure if a warning light had illuminated. The vehicle was towed to the dealer, where it was diagnosed and determined that the transmission had failed and needed to be replaced. There were metal shavings found mixed in with the transmission fluid; however, the vehicle remained with the dealer unrepaired. The contact was informed by the dealer that the warranty had expired, and the vehicle could not be repaired. The manufacturer was notified of the failure but declined to assist in covering the cost of the repair. The failure mileage was approximately 166,000.

See all problems of the 2020 GMC Sierra 2500 🔎.

The contact owns a 2024 Chevrolet Sierra 2500. The contact stated that while his son was driving 60-62 mph in tenth gear, the transmission unexpectedly downshifted to seventh gear. There was an abnormally loud clunking sound coming from the vehicle. There were no warning lights illuminated. The vehicle was taken to the local dealer, where it was diagnosed and determined that the valve body needed to be replaced. The vehicle was not repaired due to the parts being on backorder. The manufacturer was contacted, but no additional assistance was provided. The failure mileage was approximately 68,000.

While driving the vehicle, I entered onto the interstate, as I accelerated into the flow of traffic, (approximately 45-50 mph) my truck suddenly and unexpectedly jerked and “clunked” extremely hard, I thought I had ran over a large object, approximately 5 seconds later it jerked and “popped” loudly. At that time the reduced engine power and check engine light came on causing my vehicle to suddenly slow down to 20 mph and almost being rear ended by a tractor trailer truck traveling the speed limit that had to hit his brakes e trebly hard to avoid a rear end collision. After removing my truck from the flow of traffic, I turned it off, exited the vehicle to see if I had ran over something, I did not. Cranked it up, no signs on the dash, as I started back to the travel lanes, it “surged & jerked” the reduced power and check engine light came back on. Once I got the truck to the dealership, the service manager informed me he knew exactly what it was, the transmission valve body was no longer good. He also informed me that my truck was now number 28 in line just at that dealership for the same issue and repair, then added that gm is out of stock on the parts and back order status.

The contact owns a 2020 GMC Sierra 2500. The contact stated that while her husband was driving 30 mph, the rear wheels locked up and the vehicle skidded to a complete stop. No warning lights were illuminated. The vehicle was towed to the dealer, who diagnosed a failure with the transmission. The contact was informed that the transmission had imploded and needed to be replaced. The vehicle was not repaired. After investigating the failure, the contact related the failure to NHTSA campaign number: 24v797000 (power train); the VIN was included but the vehicle had not been repaired. The manufacturer was not notified of the failure. The failure mileage was 125,000.

Code p0777 – "pressure control solenoid 'b' stuck on" – reduced propulsion / reduced engine power initiated while merging onto the interstate, this code triggered a reduction in engine power, limiting my speed to 35 mph on a highway with a posted limit between 40-70 mph. Due to the limited power, I was forced to drive on the shoulder to reach the next exit and pull into a service station. I verified the code using an obd-ii reader at autozone. Subsequently, I had the truck towed approximately 1 hour and 30 minutes back home. The vehicle has been at a gm dealership since June 24th, where the faulty valve body has been confirmed. However, there is currently no estimated arrival date for the replacement part, which was ordered on the same date. To my knowledge, the part has only been diagnosed electronically and has not yet been visually inspected. The dealer plans to remove the valve body and transmission pan once the replacement part arrives. Notably, there were no prior warnings, messages, or symptoms before this issue occurred; this code and power reduction were the first indications of a problem.

What component or system failed or malfunctioned, and is it available for inspection upon request? - transmission valve body resulting in a p0700 & p0747 code. Yes currently installed in vehicle. How was your safety or the safety of others put at risk? - when the vehicle goes into a limp mode to protect the transmission and rear-wheel lock up, the truck shuttered and hard downshifted. Speed limit is restricted to 5th gear only. I've been instructed by gm to continue driving and using the vehicle until the problem happens again, knowingly putting myself and others at risk on a second failure that could happen at any time. Has the problem been reproduced or confirmed by a dealer or independent service center? yes this is a common problem with a recall #n242454440, NHTSA 24v-797. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others? mine has been rejected by gm. Although I documented and photographed the failure codes, I cleared them from the vehicle in order to attempt to safely get to the dealer and prevent further damages. Were there any warning lamps, messages or other symptoms of the problem prior to the failure, and when did they first appear? at the time of failure yes, check engine light and codes from an engine monitor coinciding with the known problems. Engine speed / power was reduced to allow only 5th gear.

Problem #1: trailer brakes failed while pulling 40' fifth wheel trailer. Was driving at about 50mph on a 55mph road and was approaching a stop light. I went to apply my truck and trailer brakes simultaneously and quickly found out I had "lost" my trailer brake. This happened another two times within the next 10 mile trip to my house. I immediately disconnected my trailer and took my truck to the shop. The GMC dealer fixed this issue, however, it is both scary and extremely dangerous to the public when something like this happens on a brand new truck. Problem #2: right around 30,000 miles I was driving (unloaded) down the road at about 35mph when I felt a hard clunk in the transmission followed by grinding noises - immediately a notice flashed on the dash stating the truck went into reduced acceleration and the check engine light came on. I brought my truck to a local GMC dealer to be serviced on June 19th and they advised me it was the allison transmission valve body. The part has been on back-order and my truck is still at the dealership sitting in the back lot with at least 4 other 2024 hd models. I called gm twice to inquire about safety recall n242454440 (covering 2020-2022 gm vehicles) and recommend that it get extended beyond 2022 since the problem with the transmission valve body has not been resolved yet. I have not heard anything back from them since that call back in June.

The contact owns a 2023 GMC Sierra 2500. The contact stated while driving 35 mph, the vehicle gear shift was shifting independently, and the contact noticed the vehicle was shaking and the vehicle went into limp mode. The check engine lights illuminated. The contact pulled over to the right side of the road turned the vehicle off and then turned the vehicle back on and the failure persisted. The contact the gear shift was stuck in fifth gear. A dealer was contacted. The vehicle was taken to the dealer where it was diagnosed that the valve body needed to be replaced. The vehicle was not repaired. The manufacturer was notified on the failure and opened a case. The contact was referred by the manufacture to report the failure the approximate failure mileage was 50,823.

I rely heavily on this vehicle for my business and within 1 year of ownership, the vehicle broke down on the highway allowing it to only run @ 30mph. After finally locating a dealer who could evaluate the vehicle in less than 1 week, I was informed that the part was unavailable and they indicated, "it could take 1 month or 3 months to receive. " following multiple conversations, I was forced to open a claim with gm customer care. While trying to get information, I was, at one point, told that "although the code indicates failed transmission control module, it doesn't happen all the time and if I wanted to drive it I could come and take it until the part arrives. " that really told me alot about how gm representatives view safety while when it happened, I was on interstate and nearly got trounced by oncoming heavy traffic while pulling an equipment trailer. After the case was handed off to several gm customer care representatives, I finally rec'd feedback including several email updates. I finally rec'd the vehicle back after 1 month and was informed that 1) would receive car payment from gm & 2) would receive additional compensation for lost work time while my vehicle was out of service (Jan 2024). Since that conversation, I did receive 1 car payment however, never heard back from alisa regarding "lost time". I have sent several emails to customer care asking for an update however, crickets. Furthermore, the car has returned to the shop for another warning to "shift vehicle to park" when it was in park. They told me its a electrical malfunction but they could not get the error to come up on test. I have a photo showing the error.

2024 GMC denali hd with approx. 12, 500 miles: the truck is constantly going into limp mode. Driving down the road, first it feels like the wheels lock up with a loud noise. Immediately goes into limp mode and check engine light comes on. Took it to the dealer yesterday 6/3/25 for repairs. I just spoke to my service advisor this morning where I was told it was the valve body of the transmission that needed to be replaced. However, they were on backorder and have no eta on when they will get a replacement.

I was driving home from work and my truck down shifted and rear wheels locked up, now it’s in limp in mode and will not shift.

Vehicle transmission locked up and brought me down to 20-30mph out of the blue at [xxx] . Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

Two times with my truck, the transmission has locked up solid while towing a heavy load almost causing my load to shift and wreck my truck in traffic. It happened at 60k miles and again at 68k miles. The truck shutters and then locks up solid on the transmission, then after a second of sliding, it releases and goes into limp mode. This is a serious issue when it is uncontrollable. It felt like my trailer had broken loose and slammed into the cab when it happened. I'm sure it wasn't good on the truck in general. A code scanner read p0747 code and it appears that Gmcs recall does not cover my truck in another recall for the same issue with 20-22 model trucks. It is happening all the way up to the 25 year models from what I read.

After the transmission recall was completed, I’m now having erratic shifting. Having the recall adding software monitoring for a hardware issue is inadequate. Now that I am out of warrentee, gm has not resolved the issue and now I am having shifting problems.

Transmission fluid overheating, which is a known issue in other gm models with 6. 6l diesel with 12 speed allison transmission. Confirmed by warning message received on dashboard and transmission fluid temperature gauge. This occurred within 3 weeks of purchase. Dealer confirmed “valve” needs to be replaced. Part is on back order with no arrival eta. Service advisor indicates the truck is not safe to drive and remains in the service department.

The contact owns a 2020 GMC Sierra 2500. The contact received notification of NHTSA campaign number: 24v797000 (power train); however, the part to do the recall repair was not yet available. The local dealer was contacted. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The manufacturer was not made aware of the issue. The contact had not experienced a failure. Parts distribution disconnect.

This issue is pertaining to the valve body in my 10-speed transmission. While I was traveling home, the truck experienced a “wheel lockup”. The transmission shifted down aggressively, then putting the truck into limp mode. I had to travel the rest of the way home with a max speed of 35 mph. I have been without this truck for 3 months waiting on parts. This is absolutely unacceptable from gm. Extremely unsave.

Shift to park message displayed while attempting to shut off engine after shifter was in the park position, accessory would not turn off even after driver door opened and could not leave vehicle.

The contact owns a 2020 GMC Sierra 2500. The contact stated that the vehicle was under NHTSA campaign number: 24v797000 (power train) and the vehicle was repaired. The contact stated that after the recall repair the transmission started shifting hard. The vehicle was taken to the dealer and the contact was informed that the transmission module would reprogram independently and adjust independently. The contact stated that a a week later while driving approximately 45 mph, the vehicle started to run rough, and the message engine power reduced was displayed. The transmission fault, parking brake system alert, service parking brake, and the check engine warning light illuminated. The vehicle was towed to the dealer who diagnosed the vehicle and determined that the fuel injector was open, causing high resistance in the connector for cylinder #4. The transmission could not be diagnosed until the injector was repaired. The manufacturer was informed of the failure and opened a case. The failure mileage was 125,000.

The contact owns a 2023 GMC Sierra 2500. The contact stated while driving approximately 40 mph, the vehicle shook abnormally twice and then switched to low power mode. The contact stated there was no warning light illuminated. The contact had the vehicle towed to a local dealer, where it was diagnosed and determined that the transmission valve body needed to be replaced. The contact stated that the valve body had failed within one and a half year. The contact requested that the entire transmission be replaced. The manufacturer was informed of the failure and declined to replace the transmission. The vehicle was not repaired. The failure mileage was approximately 42,000.

Radiator hose connection broke and loose fluid and transmission got broken.

See all problems of the 2021 GMC Sierra 2500 🔎.

2023 GMC Sierra 2500 at4 with approximately 36,000 miles as of current. The vehicle has experienced three valve body failures to date. GMC dealerships have completed one gm remanufactured transmission replacement and an overhaul of the second transmission. The third valve body has now failed. A GMC transmission specialist confirmed transmission failure upon recent test drive on 2/24/2025. GMC dealership refuses to perform warranty repair as they are stating “a recall is being developed” therefore will not repair/replace current defective powertrain parts. I was given the vehicle back with the verbal disclaimer “it should be safe to drive but the rear wheels can lock up at highway speed so be aware. ” the failure causes extreme harsh downshifting and what feels like a momentary rear wheel lock up. I have experienced this numerous times at lower speeds (<40mph). The check engine light does not come on.

Odi # 11646185 my truck on [xxx] leaked transmission coolant from the jumper line leak( which this part is recalled but not for my VIN #) $400. 61 dollars and left me stranded in the middle of the highway and had to be towed. After the repair and checking the transmission was discovered it was ruined because of the leak. So now I have to have a new transmission installed at jennings in beardstown IL to the cost of $7363. 39. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

The contact owns a 2020 GMC Sierra 2500. The contact stated while driving 30 mph, the engine revved while the vehicle lost motive power in the middle of the road. The contact was unable to pull over to the side of the road. The vehicle was restarted but was undrivable. An unknown warning light was illuminated. The contact stated that while the vehicle was being towed, there was a significant amount of fluid leaking onto the ground. The vehicle was towed to ryan's repair, where it was diagnosed with a fractured transmission cooler line. The vehicle was not repaired. The mechanic related the failure to an unknown recall. The dealer was not notified of the failure. The manufacturer was notified of the failure, but no assistance was provided because the VIN was not included in the TSB. The failure mileage was approximately 112,000.

Hard shifting. Back wheels locking up.

Transmission not shifting correctly. Have had the recall software update. Two new valve bodies and still not shifting correctly. Transmission is known to lock up.

My truck had been sitting idling for about 20 minutes on a job site on flat level ground. I turn around for whatever reason and my truck is driving forward with on one in it but my dog. The truck ran into an out rigger on my crane. I had 3 of my employees there that witnessed this happen. I got into my truck and the shifter was in drive. Somehow my dog was able to shift my truck into drive from park while it was sitting idle. I have 3 eye witnesses as well as pictures of the incident. I have pictures but was no able to upload them to they portal.

The contact owns a 2024 GMC Sierra 2500. The contact stated that transmission fluid was leaking onto the garage floor. The contact stated that while driving at an undisclosed speed, the transmission hesitated before shifting. The contact stated that the check transmission warning light was illuminated. The vehicle was taken to a local dealer; however, the dealer was unable to diagnose the vehicle. The vehicle was not repaired. The contact had inquired if the transmission needed to be replaced, and was informed that transmissions were on a national back order. The manufacturer was not informed of the failure. The failure mileage was 8,808.

The contact owns a 2020 GMC Sierra 2500. The contact stated while driving at an undisclosed speed, the accelerator pedal was depressed, and the transmission jerked. The contact stated that the transmission was skipping gear while shifting. The check engine warning light turned on and off. The contact received notification of NHTSA campaign number: 24v797000 (power train); however, the part to do the recall repair was not yet available. The local dealer was contacted. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The manufacturer was made aware of the issue. The failure mileage was approximately 114,000. VIN tool confirms parts not available.