2021 GMC Sierra 1500 Powertrain (other) Problems

I own a 2021 GMC Sierra 1500 AT4 with the 3.0L Duramax diesel. The vehicle developed severe transmission problems, including harsh/jerky shifting and a hard clunk when shifting into reverse. The vehicle was subsequently diagnosed with an internal transmission failure. The repair facility informed me that the transmission gears had failed and caused damage to the transmission and stated that the failure appeared to be related to a manufacturing issue. The repair facility also advised me to watch for a future recall because they believed this could be a widespread issue occurring in other vehicles. I am submitting this complaint so the failure can be documented and considered along with other reports of transmission failures involving this vehicle.NOTE FROM AUTOSHOP:TRANSMISSION FAILURE WAS DUE TO A MANUFACTURE DESIGN FLAW, NOT DUE TO THE CUSTOMER'S DRIVING HABITS. THE PUMP ORIGINAL DESIGN IS WITH SLANTED GEARS AND THE GEARS ARE FORCED AWAY FROM EACH OTHER AND PLACING TOO MUCH STRAIN THE BEARINGS ANI THE BEARING FAIL. AN UPDATE PERFORMED TO HAVE STRAIGHT CUT PUMP GEARS TO AVOID BEARING DAMAGE. CDF DRUM AND CENTER SUPPORT CHANGED TO UPDATED PARTS THAT ARE HEATED TREATED TO AVOID DAMAGE

NHTSA ID

11766718

Incident

Aug 18, 2026

Purchased a used 2021GMC SIERRA in Mar. 2025 from W&K GMC Sedalia Mo. Two mths ago ([XXX]) noticed an occasional slipping in transmission, wheels lock up. The truck would slip, lock for 1-4 seconds and then return back to normal driving. Has done this while accelorating and while driving down the highway. I took truck to my local repair garage who indicated it was most likely the torque converter and it would need to be taken to the dealership for repair. After mechanic commenting that he had seen several GMCs with the same problem, I looked up GMC recall and found that this issue did have a recall on 2020 - 2022 GMC SIERRA TRUCKS ( ours is a 2021)! When my VIN did NOT show any recalls, I called W& K GMC in Sedalia on 9-23-26 and spoke with the shop who told me MY truck did not have the recall notice and it would cost me $160 out of pocket for a diagnostics and $600 -$800 for a converter to even be flushed to see if problem resolved PRIOR to any part replacement. They would have to charge me full price for this repair since MY VIN DID NOT HAVE A RECALL, BUT THE SAME TRUCK MODEL, YEAR, AND ENGINE HAS OTHER RECALLS? I called GMC customer service line on 9-23-26, spoke with customer service agent Tanika, she documented the same info. and could not explain why a 2021 Sierra with the same problem as a 2020-2022 Sierra was not included in this recall that it must have been manufactured in a different facility? The fact that my local garage mechanic in a very small town, has already seen SEVERAL GMC trucks with the SAME PROBLEM, leads me to believe this is a WIDE SPREAD PROBLEM, that GMC is choosing to ignore due to the cost of repairs involved. I am requesting an investigation into HOW MANY RECALLS HAS GMC SENT OUT AND REPAIRED? AND SPECIFICALLY WHY AFTER 3 YRS OF PRODUCTION BY GMC DO THEY BELIEVE A TRANSMISSION PROBLEM WAS ONLY CERTAIN VEHICLES AND NOT ALL THE VEHICLES? This is a huge safety concern if wheels lock up on hwy at 70mph due to malfunctioning TC INFORMATION REDACTED PURSUANT TO THE FREEDOM OF I

NHTSA ID

11766353

Incident

Aug 10, 2026

Transmission failed, Value Body is listed by dealer as the cause. GMC is saying that my vehicle is not part of the recall, even though it is part of the same model, same years as well as the same problem, the value body on the transmission. See estimate from dealership Tucks GMC Hudson, MA TRANSMISSION REPLACEMENT WITH BYPASS VALVE $6800.00 RADIATOR REPLACEMENT LEAKING $1980.00 ABS TRACTION LIGHT WHEEL SPEED SENSOR $395.00 CHECK ENGINE LIGHT IS ON NEEDS PCV VALVE HOSE AND SOLENOID $430.00 OIL LEAK BETWEEN ENGINE AND TRANSMISSION ?

NHTSA ID

11762717

Incident

Jun 12, 2026

Rear wheel lock up. Very unsafe. I am on my 3rd valve body for my transmission. GM doesn’t want to replace transmission but will warranty for 150k miles. I bumped a semi during one of my lock ups.

NHTSA ID

11760336

Incident

Jul 16, 2024

For close to one year, there feels like a catch, grind, stall, or slight shake, mostly while the vehicle is shifting gears, made worse or noticed more by higher speeds like driving on the highway vs. slow city streets. It's difficult to explain or assess so not sure if it is the engine or transmission. With the open recall from GMC on some vehicles with the same engine as mine it is concerning that maybe it should have been included.

NHTSA ID

11759464

Incident

Oct 1, 2025

Transmission Valve Body failure. - Caused wheels to lockup momentarily and killed the engine with sudden loss of propulsion. Link to video of incident: [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11756447

Incident

Aug 4, 2026

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the transmission was shuddering, especially while driving uphill. The dealer was contacted, and the vehicle was diagnosed and determined to have a failure associated with a GM TSB for the incorrect transmission fluid inside the transmission reservoir. The vehicle was not yet repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 38,875.

NHTSA ID

11754985

Incident

Jul 15, 2026

Mileage

38,875 mi

2021 Harley Davidson Sierra 4WD, 6.2L L87. Started the truck in the morning and immediately heard intermittent, very loud banging noise coming from engine. Shut truck down quickly and had it towed to dealer. Diagnosis was bent pushrods & failed lifters which were replaced under warranty. Factory warranty expired only 4 months after this failure, and the recall does not include my VIN so I did not get an extended warranty or any other protection. GM has yet to even reimburse the tow bill. Completely unacceptable for a truck that was well over $100k when new.

NHTSA ID

11753693

Incident

Oct 11, 2025

On June 25, 2026, at approximately 84,000 miles, while traveling approximately 60-65 mph on Highway 121 in a posted 65 mph zone, driving my 2021 GMC Sierra 1500 AT4 equipped with the 6.2L L87 engine, multiple warning messages suddenly appeared, including “Check ESC,” “Check Parking Brake,” “Check Brakes,” and “Check Engine.” The engine began operating abnormally. I drove directly to Sewell GMC because I was concerned that the engine could fail or the vehicle could lose propulsion while in traffic. There was no crash, fire, or injury. Sewell GMC inspected the vehicle and confirmed catastrophic internal engine damage. The technician found metal debris in the engine oil and oil pan, damaged internal bearings, and camshaft/lifter damage. Sewell advised that the complete engine must be replaced. The vehicle remains at the dealership, has not yet been repaired, and the engine and failed components should be available for inspection. Before this incident, I had not experienced warning lights or symptoms indicating that an imminent catastrophic engine failure would occur. GM and the dealership advised that my VIN is not included in the current L87 engine recall because the engine was built in 2020. However, the diagnosed bearing damage, metal contamination, and catastrophic engine failure appear similar to the engine failures addressed by that recall. I am reporting this because an unexpected internal engine failure while driving creates a serious risk of loss of propulsion and a collision.

NHTSA ID

11752087

Incident

Jun 25, 2026

The 10 speed automatic transmission shakes and jumps between gears. The transmission also shakes and rumbles at cruising speeds. The diesel engine version of this truck is already recalled. My truck is a gas engine and should also be recalled. This is the same defective 10 speed transmission used in all GM vehicles and recalled in many. This vehicle needs to be recalled and fix before the wheels lock up and kill someone.

NHTSA ID

11750566

Incident

Jun 1, 2026

transmission shuddering, harsh or delayed shifting, and erratic gear changes. The truck jerks really bad during each shift of the ten speeds. A vibration or shudder typically occurring at speeds between 25-65 mph under light throttle. Also makes a bad noise every times it’s shifting. I have no lights on the dash and the gmc app tells me everything is fine when clearly it’s not . I see there’s a recall for my year and make but for some reason my vin doesn’t fall in the category

NHTSA ID

11749233

Incident

Dec 31, 1969

My car suffered a catastrophic engine failure, metal schards were found in the oil filter and was left out of the 2021 recall 25V274. The in service date of vehicle is March 13, 2021. The car was 83 days out of warranty when the engine failed. The truck has 47,000 miles on it. They are now trying to charge us, barter with us. They have gone from $2800 for repair, negotiated down to $100 to sign this off as a good will repair stripping us of lemon law rights and future recall remedies. Car is currently sitting at the dealership.

NHTSA ID

11749076

Incident

Jun 4, 2026

Dashboard lit up with engine light and stated that there's no compulsion

NHTSA ID

11748647

Incident

May 21, 2026

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the brake pedal was depressed, but the vehicle continued to move forward. There was no warning light illuminated. The vehicle was taken to the dealer and was diagnosed with transmission failure. The contact stated that the valve body and torque converter needed to be replaced. The dealer informed the contact that the transmission might need to be replaced. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 65,561. The VIN was unavailable.

NHTSA ID

11745943

Incident

Jun 12, 2026

Mileage

65,561 mi

While driving my vehicle, the engine and transmission lost power and the check engine light came on. The vehicle went into limp mode and engine propulsion was limited. Had I been traveling at a faster speed, this would have been very unsafe. After coming to a stop, placing the transmission in reverse did not move the vehicle and there was a grinding noise. I was able to savely move forward in limp mode, but the shifting was harsh. I was able to find an empty parking lot to safely park. The truck was towed to Jim Winter dealership in Jackson MI for inspection.

NHTSA ID

11744736

Incident

Jun 17, 2026

So I made an appointment to have my truck recalled and the Wednesday before I took it, and it cranked no start and I called the dealership. Ask if they had any other those like this and they said that it could be the fuel injector module and so I got it to a mechanic shop to read the codes and it gave me a code p062b and I asked the dealership to look into it and they never figured out what we were not wrong. I just testing the battery. Well, then I got it back after the recall was done and new transmission valve body put in and about 30 miles down the road it started to shake violently and had a flashing engine light so I got it home called the dealership the next morning because they were closed set up another appointment got it to the dealership dealership said it had a couple misfires but since it wasn’t over 100 they weren’t concerned even though I’m pretty sure it is related to the fuel model going out because it has been cranking rapidly whenever I try to start it, but they won’t do anything to figure out what’s wrong?

NHTSA ID

11744628

Incident

Jun 5, 2026

When pressing on the gas, especially when moderately accelerating, the truck experiences severe shaking, which interferes with acceleration, as well as causing the truck to "jump" when the transmission gear "catches", even while driving. When the truck is at a full stop and the engine is auto off, when it restarts, it does so frequently when it reengages that it causes a physical "jump" in the vehicle, causing the driver's foot to come off the brake pedal. This has been most noticeable since my vehicle hit about 70k miles. I currently have 84k miles. I engaged the dealer and was told the transmission is out of warranty. I see that other GMC Sierra models suffer similar problems and recalls have been issued to GMC that they must repair those vehicles. Despite that, my vehicle is not included in any current recall program.

NHTSA ID

11744554

Incident

Jun 15, 2026

While coasting down or under very light acceleration between 12-20 mph the vehicle has a shudder like driving over a highway rumble strip. While cruising on the highway at 65+ mph, the vehicle has a light shudder or vibration. Vehicle has been checked numerous times for wheel and tire inconsistencies. Brake pads and rotors have also been replaced with no change in issue. Headlights daytime running light changes color from bright white to purple during warm weather. The vehicle has been to 3 different GM dealerships and they acknowledge the issues but do not provide a resolve.

NHTSA ID

11743882

Incident

Jun 13, 2026

power steering locked up while driving. has been inspected and repaired by manufacturer. recall.

NHTSA ID

11741190

Incident

Mar 29, 2026

power steering locked up while driving. multiple dash lights turned on, on its own after the issue, 4wd, emergency brake, abs, and other ones im not sure what they are. took it to the dealership for a recall and told them the issue that happened.

NHTSA ID

11741189

Incident

Mar 29, 2026

The truck randomly will not detect that it was shifted into park. Shifting between gears and back to park does not automatically fix the the issue and has taken up to 10 mins to turn the truck off. The adaptive cruise controls stopped working and can still use regular cruise control. Just not adaptive. It appears greyed out. The truck has thrown the error code: P1098, Engine Coolant Control Valve Position Sensor Minimum Stop Performance. The truck would go into limp mode until the error was cleared. This error has appeared 4 times over the past five months. The most recent date of it happening was today. 06/30/2026

NHTSA ID

11741078

Incident

May 30, 2026

The truck has a studder that comes from the transmission when at highway speeds. the studder can be felt at random intervals (seconds) from all passengers. The studder is also present on starting up a slope or accelerating from a stop at a slow pace. when accelerating slowly the jerk is more prominent. We have taken it to the GM Dealership, they confirmed the issue was present. The dealership said the GM guidence was to 1st try a re-program and then replace the torque converter. The program flash was unsuccessful, then we paid $4000 to change the torque converter. The Tech stated that this was the GM suggested fix, but noted that we are changing the fluid also which could mask the issue if it is the valve body causing an issue. The replacement torque converter and fluid did somewhat reduce the issue for a short period of about 2 months before it has returned as it did before. The next option from the dealership is in excess of $8,000 for a remanufactured transmission which is outside our reasonable spend, when we dont expect the remanufactured transmission will have any better valve body components. The recent recall did not cover my gas 6.2L sierra 1500, although it clearly is insufficient stating that it just a warning that there is a safety risk present. The valve body of the transmission appears to be an issue across all models and the recall addresses that it is present. We continue to drive this as the primary family vehicle with the hesitation and jerking present as GM dealer offered no support other than $8,000 remanufactured transmission on top of the $4000 we already spent. I believe the recall was insufficent in covering the Gas models with the exact same transmission and known issue. I also believe the offered solution continues to put those driving at risk.

NHTSA ID

11740118

Incident

Apr 1, 2025

Right after i bought the car I had a very bad misfire on cylinder 1, the car would shake at idle. Took to dealership and they said they replaced all the spark plugs and replaced cylinder 1 coil. about a week later the misfire and shaking started again but this time it would come and go. the check engine light would be on then it would go away for a bit and then come back on over and over again. The only thing that seemed to work is if i disabled the stop and go start system and put the car in L9 to disable the AFM. This seems to work and I have since bought a disabler for these systems. However, there is still a vibration at idle and i feel that its a temporary fix to a bigger issue. This is my daily driver and constantly have my children in the car and just want the car to be safe for everyone. The transmission downshifts rough and at times seems to slip/lock up while driving. I haven't brought it to the dealership for this as of yet.

NHTSA ID

11737211

Incident

Jun 1, 2025

Coolant control valve has failed and caused the check engine light to occur is available for inspection. Could cause the car to overheat and cause harm to myself or others Yes has been confirmed by dealer No GM has a special coverage out for the specific vehicle and model years for this vehicle, but are stating that my vehicle does not pertain to that coverage.

NHTSA ID

11735894

Incident

May 3, 2026

While driving into work, I noticed a knocking sound from the outside of the vehicle. Once parked, upon further inspection I narrowed down the area of the noise to the bottom rear of the engine/front of transmission. Fortunately, I was able to park in front of my office building and wasn’t stranded on the side of the road but under different circumstances it could've been the side of a busy highway or hours from home. I had the vehicle towed to the dealership I originally purchased from, the dealership was able to duplicate the issue with me present. Later that afternoon I was informed that the engine had failed and a replacement would be ordered. There was no prior indication of a problem or warning/CEL’s. The engine failed after the dealership had completed the engine recall ( pico test and 0-40W oil change ) related to the vehicle. I am reporting this in hopes that it helps with the investigation. This has been very disappointing for me as I have supported the brand of vehicle for many years. Only to have many issues under 80,000 miles and to lose confidence in the vehicle I purchased and the company.

NHTSA ID

11731720

Incident

Apr 15, 2026