Power Train Problems of GMC Sierra 1500 - part 1

The transmission overheats on this vehicle shutting the vehicle into “limp mode” this is extremely dangerous when at interstate/highway speeds and the vehicle slows it self down to a dangerously low speed and all other vehicles around are traveling at a high rate of speed, this has happened twice, it has also happened while in back roads and tractor trailers have had to swerve to avoid a collision.

See all problems of the 2021 GMC Sierra 1500 🔎.

While turning right and at a slight incline the truck engine turned off, the transmission made a grinding noise, the truck went into neutral and the dash stayed “press start button”. This is the second time this has happened within 5000 miles of the struck being purchased. Several others have reported the exact same issue on facebook forums.

Engine stall on the highway.

The vehicle in questions was purchased with less than 5 miles in year 2020. This vehicle was dropped off at mac haik chevolet madison ms on September 25, 2026. I was advised on September 28, 2026, that the vehicle was test driven with the scan tool connected, graph torque converter slip, found over 100 rpm slip when torque converter engaged and causing shutter at highway speeds, also felt 1-2 and 2-1 harsh downshift, check fluid condition was black and smelled burnt, replace transmission assembly, flush cooler, program transmission control module and perform clutch fast learn. Estimated cost of $8k.

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The contact owns a 2022 GMC Sierra 1500. The contact stated that while driving 25 mph, the contact entered a parking lot and shifted the vehicle into park and the message “shift to park” was displayed. Additionally, the check engine warning light illuminated. The contact stated that the failure had occurred on several occasions. Due to the failure, the contact was unable to start the vehicle. The failure mileage was approximately 74,000.

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Power steering seems to be lost for a second or two at low speeds turning. Happens multiple times a day.

See all problems of the 2015 GMC Sierra 1500 🔎.

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.

See all problems of the 2023 GMC Sierra 1500 🔎.

Very similar to NHTSA complaints 11752469; ?11762072?; 11761966?; 11761844; ?11755200 while turning left into my 6 degree inclined drive at a slow rate of speed under 5 mph, my 2026 GMC sierra slt x31 with 1500 miles suddenly slams into park and shuts down. "press start" shows on display and am able to start the truck. Twice the "service transmission" light has displayed. I took it to the dealer after two incidents and they could not replicate. Since getting it back from the dealer, I've had six more incidents and am taking back to the dealer with more information for them. The last incident, I was prepared for it and felt the truck begin to shut down and slammed on the brake before it shut down.

1. I am being told that the high-pressure fuel pump (hpfp) catastrophically seized and locked up internally while driving. Because the hpfp on the 3. 0l duramax (lm2) engine is directly driven by the engine's timing system, this sudden mechanical seizure instantly destroyed the engine timing gears and snapped/skipped the timing chain. The failed components are currently intact inside the vehicle and are fully available for inspection upon request at ron’s smith GMC in merced, CA. 2. The failure occurred on busy labor day (xxx) while our family of [xxx] was traveling back home at 70 mph on a major highway. The truck violently shook, instantly lost all engine power, and forced the vehicle into a dangerous limp-mode state before completely stalling in live highway traffic at night around 10:45 pm. This sudden loss of propulsion at high speed severely compromised our ability to safely navigate out of the way of fast-moving highway traffic, creating an immediate & extreme risk of a high-speed rear-end collision. At times hazard lights didn’t work causing family panic & screaming as truck shook with passing traffic. 3. The problem has been officially confirmed by ron smith GMC in merced, CA. Their service department diagnosed the issue, confirming that the high-pressure fuel pump had locked up and subsequently destroyed the timing belt/chain and engine gears. 4. The vehicle and its failed components have only been inspected by technicians at the ron smith GMC dealership service department. No police, insurance representatives, or outside third parties have inspected the vehicle yet. 5. I had been extremely happy with my truck and there were absolutely no warning lamps, dashboard messages, or driving symptoms prior to the failure. The truck was operating perfectly normally under cruise until the exact moment of the failure, at which point a "reduced engine power" warning flashed on the dashboard simultaneously with the mechanical lock-up, shaking, and immediate stall. Information redacted pursuant to the freedom of.

1. I am being told that the high-pressure fuel pump (hpfp) catastrophically seized and locked up internally while driving. Because the hpfp on the 3. 0l duramax (lm2) engine is directly driven by the engine's timing system, this sudden mechanical seizure instantly destroyed the engine timing gears and snapped/skipped the timing chain. The failed components are currently intact inside the vehicle and are fully available for inspection upon request at ron's smith GMC in merced, CA. 2. The failure occurred on busy labor day (xxx) while our family of [xxx] was traveling back home at 70 mph on a major highway. The truck violently shook, instantly lost all engine power, and forced the vehicle into a dangerous limp-mode state before completely stalling in live highway traffic at night around 10:45 pm. This sudden loss of propulsion at high speed severely compromised our ability to safely navigate out of the way of fast-moving highway traffic, creating an immediate & extreme risk of a high-speed rear-end collision. At times hazard lights didn't work causing family panic & screaming as truck shook with passing traffic. 3. The problem has been officially confirmed by ron smith GMC in merced, CA. Their service department diagnosed the issue, confirming that the high-pressure fuel pump had locked up and subsequently destroyed the timing belt/chain & engine gears. 4. The vehicle and its failed components have only been inspected by technicians at the ron smith GMC dealership service department. No police, insurance representatives, or outside third parties have inspected the vehicle yet. 5. I had been extremely happy with my truck and there were absolutely no warning lamps, dashboard messages, or driving symptoms prior to the failure. The truck was operating perfectly normally under cruise until the exact moment of the failure, at which point a "reduced engine power" warning flashed on the dashboard simultaneously with the mechanical lock-up, shaking, and immediate stall. Information redacted pursuant to the freedom of.

Lifters and camshaft failure, loud clanking, & sudden power loss on the 6. 2 motor are the first noticeable signs. Instantly when everything happened check engine light, cruise control, & stabilizer lights flashed. The sudden loss of power forced the vehicle to suddenly slow down forcing my camper into the truck. I was hauling a within weight standerd camper but had difficulty bringing both the truck with the camper to a safe stop. There were no early signs or signal prior to sudden cautostrophic engine failure & all service records have been completed by a gm certified service dealer.

See all problems of the 2024 GMC Sierra 1500 🔎.

The contact owns a 2026 GMC Sierra 1500. The contact stated that while slowly driving up a slightly inclined drive port and making a left turn, the vehicle shut off and the parking brake was activated or the vehicle suddenly decelerated. The contact stated that the failure had occurred on several occasions with three separate identical vehicles, including the loaner vehicle provided by the dealer. During the failure, the messages "press start" and "service transmission" were displayed. The vehicle was taken to the local dealer who was unable to determine the cause of the failure. The manufacturer was notified of the failure. The failure mileage was 29.

Powertrain issues and a chassis issue that is extremely dangerous. Tailgate on rare occasions falls open by itself. There is a design flaw in the placement of the catalytic converters. The heat is burning up the fluid. I could not believe my eyes when I serviced the transmission. This is another shortcut by gm to save on the extra wiring needed for the oxygen sensors (2)in the converters and the two oxygen sensors downstream of the converters. There is plenty of room for the converters further down by the tail shaft to drive shaft connections. This is gm’s way of being cheap. Here’s the problem. The converters get way too hot. The fill plug for the transmission which is behind a low rent heat shield crumbled into my hands from excessive heat buildup. Gm knows there is a problem with the fluid breaking down. Their bandaid answer is to use mobil 1 fluid instead of the recommended dexron 6. What needs to happen is a safety recall issued for the unwanted tailgate deploying all by itself. There needs to be a redesign in the exhaust system. The transmission (8 speed) has a catalytic converter exactly on both sides and the crossover pipe runs directly under the transmission sump pan. No wonder they are having issues with transmissions burning up. This is a fire hazard !!! with the converters being so close to the exhaust manifolds, a leak from the engine or the transmission would be enough to ignite and possibly kill the occupants. All in the name of saving a few cents in wiring. Myself, I am a retired gm mechanic. I started working at sewell Cadillac in [xxx] in 1975. I have held the title of ase master tech. Cadillac master tech. I have been a gm shop foreman and a gm service and parts director in my career. I retired from federal express as in charge of fleet maintenance and gse(aircraft equipment). I have certifications from mercedes, BMW, Toyota, commander loaders, goodyear, and more. Given the right set of circumstances, it could end very badly. Dangerous truck ! information redacted pursuant to the freedom of inf.

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 NHTSA 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 NHTSA’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).

Purchased above listed vehicle new in September of 2023. Immediately noticed a 'coolant' smell in cab. Brought vehicle in for coolant smell issue on 12/06/23, 01/10/24, 01/16/24 and 01/23/24. We were told that there was no issue until finally on 01/23/24 we were told the radiator needed to be replaced at our expense. September of 25 we received a letter from GMC advising the "engine coolant control valve" may fail. In September of 26 while driving on mountain roads (we live in pagosa springs) 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.

I purchased a 2024 GMC Sierra 1500 denali VIN # [xxx] on xxx with approximately 18,599 miles on the vehicle. The incidents are identified below in order. 1) xxx, vehicle engine failure while driving at high speeds, with my daughter as a witness. I reported the incident to elder Ford on xxx, and my sales associate told me to take it to GMC for factory warranty. Xxx took the vehicle to central Buick GMC they performed a test that found no codes and replaced the fuel pump module from past experiences. They let me take the vehicle home. 2) xxx vehicle engine failure while driving at high speeds, had to get it towed to the dealer for repair. Again, they found no codes. Had it for 5 days. Made me take it home. 3) picked it up on xxx , was driving home and the same thing happened while going 70+ mph on the interstate. Stalled again. Drove it back to the dealer and dropped it off again, same day on the xxx. 4) again, they found no codes and made me pick it up on xxx I was driving home on xxx and the same thing happened- lost complete power while going down the road at 40+ mph. I had to get it towed the same day back to the dealer where it currently is at. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

My truck has the same issues for the transmission and engine problems I have taken it to 4 dealerships and they all say the same thing. The first one I spent about 3 hours there and they changed the 20 oil to the 40 oil and said that will fix the issues but it hasn't I called GMC to report this and they sent me to the others but they said it's been looked at and I know one of them didn't do anything to see the issue. GMC called the other day and I told them I will let the engine locked up or the transmission keep doing the same thing and they'll have to fix the issue then. I do have 109000 miles on it but thus issue has been going on for 4 years they said I have 150000 miles for the issue but I do t think that is right. I paid them cash money for the truck when I bought it.

After numerous attempts getting gm to finally look at why my vehicle because after the l87 engine swap, which failed after the pico test and oil, oil filter, and oil cap change my truck has been dangerous to drive. It falls on its face when taking off or driving. It acts as if something is holding the truck back. It takes more throttle to get it moving. Then in traffic while moving it randomly lunges forward very quickly as if I have the gas pedal to the floor. I came very close to rear ending a deer park police vehicle. They told me to get my own alternate transportation and they would then look at it. I had to go out and get a rental car. I had no choice. I explained due to my high medical bills following a cancer diagnosis, I could not afford a rental and my appointments. They basically told me come see them when I can make my arrangements. So, I rented a car, took the truck in, four days later I was told that the problem was my adas camera. I told them it worked fine before yall had it 3 months waiting on an engine. They told me I would have to pay around 1000 dollars to have my truck repaired. Even though it was clearly something they did. I made arrangements to pay them. I picked up my truck. That evening I was happy. Well, the next morning while going to get coffee the problem returned. I took it back to the dealer. I was again told, go get another rental and leave it here. I have done that. Well, that week went by. I had to borrow money to get the rental for another week. So, I could make it to my cardiologist today. I have to get cardiac clearance before I begin surgery oct. 1st. Between now and then, I have an appt with pain mgmt. , a pet scan, and an echo/doppler for cardiac clearance. Surgery begins oct. 1st. This has been making it very difficult to manage appts. With gastrointerology, cardiology, oncology, infusion services, pain mgmt. , therapy with a psychiatrist, my new esophogealist (for surgery). And follow-ups and blood tests. This is ongoing.

I am the owner of a 2019 GMC Sierra 1500 4wd equipped with the 6. 2l l87 v8, VIN [xxx], currently at 177,271 miles. On [add date] while driving 40-45 mph westbound on [xxx] near xxx in [xxx], in a school zone, the engine suffered sudden catastrophic internal failure with complete loss of propulsion and would not restart. No prior warning lights or low oil pressure warning. Vehicle required tow from school zone. GMC dealer inspected and verified catastrophic internal failure. Dealer stated verbally failure is either camshaft broken in half or timing chain sprocket/pulley broken off or loose causing timing chain to come off. Timing cover was not removed to confirm. Dealer stated engine is not repairable and quoted $13,500 for new engine replacement only. I have copies of the work order and the dealer's written statement verifying internal failure and replacement recommendation. Engine and vehicle have been retained. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

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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.

Unknown.

See all problems of the 2018 GMC Sierra 1500 🔎.

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.

My 2022 GMC sierra started hesitating two weeks ago between the speeds of 17-35 mph. It also hesitates going downhill. When I try to accelerate it hesitates causing a serious safety issue for me driving. I cant trust to move when I need to move across a busy intersection with semi tractor trailers coming at me. I can trust it to tow or haul anything anymore. This is well known and documented problem general motors has and the company deems it "normal operations" which is totally not normal.

I got the vehicle with 60,000 miles 8,000 miles in vehicle gave me problems gave me a check engine light code p0300 then took it to get inspected then was told it was the fly wheel then it’s started knocking vehicle is currently not being droven because of the fly wheel.

Vehicle: 2026 GMC Sierra 1500 at4 (3. 0l lz0 duramax diesel) current mileage: ~16,500 miles check engine light status: no check engine light active description of incident & symptoms: •interstate incident: while driving at highway speeds, a severe drivetrain vibration occurred (felt like a rear wheel weight flew off). •dashboard warnings: within 5 minutes, intermittent "traction control" and "forward collision warning" alerts appeared on the dash, accompanied by a sudden drop in engine power. •engine noise & idle: once safely pulled over, the engine exhibited a loud mechanical knock and a very rough, unstable idle. •extended crank: after shutting the engine off and waiting a few minutes, restarting the truck took roughly twice as long as normal (long crank/delayed start).

The catastrophic power failure with no warning on my 2017 GMC sierra, at 87450 miles completely contaminated the engine oil cooling lines with metallic debris and fractured structural mounts. The servicing dealership replaced the transmission but is refusing to remediate the engine line contamination without out-of pocket payment. The vehicle cannot be safely operated without causing terminal engine failure on the highway, creating a imminent mechanical and traffic safety hazard.

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I was driving north/east on [xxx] just outside of [xxx]. After accelerating to give another driver room to move out of his lane that was ending, I lost propulsion/power. The sierra went into neutral and told me something like "press start to resume". I had to immediately get off the interstate as I was rapidly losing speed. I was able to pull over to the shoulder of the interstate on the right, just before exit 2. After getting the vehicle parked, I was never able to restart the vehicle. The motor would not turn over. The display screens kept cycling between a blank display and a display that looked like the vehicle was on but the engine never turned on. When I tried to start the car, I got a message of "conditions not correct for shift". We could not even get the vehicle into neutral. I used onstar to get state patrol to show up and put lights behind us for safety. Onstar should have a recording of this call. This was on Saturday xxx in the ballpark of 2:30 pm central time. I would imagine the officer also filed a report, but I did not get it. The vehicle was towed to billion GMC in iowa city. Billion GMC said their initial suspicion is the 6. 2l motor failed / locked up on us as this is know issue that is subject of a class action lawsuit. These vehicles are not safe to be on the highway, someone is going to get seriously injured, please do everything you can to get these 6. 2l engines off the road before someone dies. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

Engine started knocking at 18k miles and took to dealer and they found metal in the filter and installed a new engine and also replaced the midplate gasket on the valvebody due to a harsh downshift without codes in the system this engine is going on 2k miles and it seems to be fine now but the problem with 6. 2 was only supposed to be on the 21-24 models and mine is a 25 model and already had a replaced and nothing from gm was said to extend the warranty on this model and powertrain.

See all problems of the 2025 GMC Sierra 1500 🔎.

I own a 2018 GMC Sierra 1500 v8 5. 3 liter which is at 46, 433 miles. Over the past few weeks I have noticed the transmission having difficulty shifting in first gear and lurching, and making shuddering noises, and as well making a constant ticking noise. After an experienced mechanic had put a diagnostic system onto my truck, his system diagnosed a transmission lifter failure, specifically 2 out of the 8 lifters. A few days later (9-04-26) I took my truck to a certified GMC servicing business (patriot Chevrolet of hopkinsville ky 270-886-1207) and had a transmission servicing done. I had told the customer service representative amanda williams about the ticking and that I thought 2 lifters going bad in the transmission were the source of it. 3 hours later the servicing was done which cost $ 474. 43. She did not know if the ticking had stopped or not. I started my engine to head home and the ticking was still happening. Nothing had changed. I got home, parked and have not started the engine since to minimize any further damage. I have become aware that this year, make and model has become infamous for the engine/transmission design and parts failure which has been at the center of thousands of class action lawsuits. I have owned this vehicle since inheriting it from my late father for 2 months before he developed dementia and suffered a broken hip. I have religiously had the oil changed every three months regardless of the mileage, and this is a sealed transmission which cannot be worked on by someone but a certified GMC mechanic, which wasn't a worry because the truck's manual says doesn't need to be worked on unless there seem to be problems. Which is what I did on 9-4-26, hoping that a servicing would fix the issue. During the 5 years that I have owned this truck, I never received any sort of notice from GMC that might've hinted at possible transmission failures, though GMC has been totally aware of. Sudden power loss dangerous and unfairly expensive to drivers.

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.

I own a 2025 GMC Sierra 1500 denali equipped with the 6. 2l v8 l87 engine, VIN [xxx]. The vehicle had approximately 35,000 miles when the engine experienced a catastrophic engine failure. Prior to/during the failure, the vehicle experienced abnormal engine noise and a loss of power. Multiple warning/alarm lights appeared on the dashboard, including the check engine and traction control warning lights. The engine failure resulted in a loss of motive power and made the vehicle unsafe to operate. Phone# [xxx] the sudden loss of engine power while driving created a serious safety hazard because the vehicle could no longer operate normally in traffic and could potentially cause a crash. I am requesting that NHTSA document and investigate this engine failure as a potential safety defect involving the gm 6. 2l l87 engine. I am also requesting that NHTSA determine whether 2025 GMC Sierra 1500 vehicles equipped with this engine should be included in an appropriate safety recall or other corrective action. The vehicle is a 2025 GMC Sierra 1500 denali with approximately 35,000 miles. The engine failure and warning lights occurred during normal vehicle operation. The vehicle and repair records can be made available for inspection, and I can provide dealer repair orders, diagnostic information, photographs, and other documentation concerning the failure. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

Was traveling home and started losing power going up a hill on xxx. The truck was surging, the check engine light came on and an audible warning of no (low?) oil pressure. The truck shut off on a busy interstate highway and barely got onto the shoulder. The tow truck driver had to lay on the ground with part of his body in the lane of travel to place "skids" under the rear tires because there is no way to place this vehicle in neutral for a tow without a special gm tool. When I contacted harry robinson GMC service center in [xxx], they told me that it was no longer a safety recall because the truck had passed diagnostics and new, high viscosity oil was put in the truck xxx. The GMC app says code p0016 which is the dreaded 6. 2l camshaft to crankshaft alignment that accompanies engine component failure. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

Ever since I bought this truck new, I noticed a lot of metal shavings and debris in the oil filter every single time I changed the oil. I took it to the dealership multiple times to have this looked into before the engine recall came out. The dealership took pictures of the metal and sent them to a general motors engineer, but the engineer just told them it was "normal. " later on, the truck went in for the official recall inspection, passed the pico test, and nothing was fixed. Then on August 4, 2026, I was driving on a crowded expressway right through a construction zone with absolutely no shoulder to pull over on. Out of nowhere, the truck started hesitating badly, lost power, and the engine started making a really loud knocking noise. It was barely running, and it was incredibly dangerous because there was nowhere to go and traffic was heavy. Luckily, I was able to limp the truck along just far enough to clear the construction zone and pull over safely.

The contact owns a 2026 GMC Sierra 1500. The contact stated that while her husband was driving approximately 10 mph, the vehicle unexpectedly shut off and independently shifted into park(p). The contact stated that previously, while the vehicle was idling in a parking lot, with air conditioner activated, the auto start/stop feature engaged, and the vehicle shut off. The message “service transmission” was displayed. The vehicle was taken to a local dealer and was diagnosed with transmission failure. The vehicle was not repaired. The manufacturer was not contacted. The failure mileage was approximately 2,000.

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).