general problems of the 2018 GMC Sierra 1500 - part 1

I’ve gone through two transmissions on my 2018 GMC Sierra 1500 both times the same issue. The gears are shot, hard shifting. Vehicle is well maintained. Both transmissions one original equipment and second bought at the dealership the truck was bought both only lasted over 80000 miles. Driving the truck loss of power or torque is noticed, then a hard shifting. Checked fluid all was good not seeing metallic shavings. Then the overheating of the transmission, faulty valve replaced with aftermarket bypass and did transmission flush. But each occasion there was an incident I would’ve driving on the interstate and vehicle would lose power and almost hard stop and cause a crash. Then vehicle would only go in reverse both times the transmission gave out. The only warning light that ever came on was a transmission overheating and nothing else. I’m currently in the process of having to get another transmission because of the same issue again. Vehicle was seen by a technician and deemed the transmission was shot again.

The contact owns a 2018 GMC Sierra 1500. The contact stated that while driving at various speeds, there was an abnormal vibration in the steering wheel. There was no warning light illuminated. The contact stated that the tires were replaced, and the wheels and bearings were inspected by an independent mechanic, but no failure was found. The independent mechanic related the failure to an undisclosed transmission recall; however, the dealer informed the contact that the VIN was not under recall. The vehicle was not diagnosed or repaired. The manufacturer was notified of the failure, but no assistance was provided. The failure mileage was approximately 28,000.

The contact owns a 2018 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle was shaking abnormally. No warning light was illuminated. The vehicle was taken to the dealer to be diagnosed, and it was determined that the engine needed to be replaced. The vehicle was then taken to an independent mechanic, who determined that the torque converter had failed. The torque converter was replaced, but the failure persisted. The vehicle was taken back to the independent mechanic, who replaced the torque converter a second time. The manufacturer was not made aware of the failure. The failure mileage was approximately 140,000.

I have 125,000 miles on my truck. I was traveling with my grandkids in the back seat. We were going through a four way stop. My truck started tapping like a lifter issue. The next thing I know is the truck engine light started flashing and car started to shake. Then, my truck lost all power and a big cloud of blue smoke came out of the tail pipe. The truck could not be driven any further. The symptoms: engine tapping, low oil, engine light flashing, shaking, lost all movement, and a cloud of smoke we had to tow my truck to the dealer and they are still accessing the issue. All symptoms are identical to the current recall of the GMC engines.

2018 GMC sierra started having shuddering/jerking/jumping problems at around 60k miles. This problem occurs while driving on straight aways, going uphill and while in drive at a stop sign/light. When the gas is accelerated the truck then hesitates and jerks/jumps. We have taken it to the GMC dealership and paid for the diagnostics and were informed “the problem wasn’t severe enough”. The truck has only been serviced by GMC dealership. So after failed attempts with GMC service department we have taken it to a local small auto shop and they automatically said it was the drive train and needed to be taken to a transmission shop. We have been gm owners for decades and are so disappointed in the service received from them.

I own a 2018 GMC sierra denali ultimate, the truck has the 6. 2 engine which had the lifter issue as stated with the current situation. At the time, the truck had 37,000 miles when the issues started. I purchased the truck from andy mohr with 8806 miles on it in November of 2019. I worked overseas for the dod so that’s why the miles are low. After I got it fixed, ($4500 dollars at hare Chevrolet) I experienced the transmission shake while driving home from work with my children in it. The transmission was shaking so bad the whole cab was rocking. That repair was $3,300. Now, the truck has piston slap and rod issues and currently at hare Chevrolet for service. I was told I need a full rebuild ($12,000 dollars or a new engine $14000 dollars). As a retired air force veteran, I didn’t expect issues like this, especially when I baby the truck and it currently has 40,530 miles. I had regular oil changes and service, yet now stuck with a high class truck that has serious issues that seem to be ignored by gm and andy mohr GMC. Andy mohr sold me an extended warranty at time of purchase but I paid for a year and a half that wasn’t usable. If I had that warranty I would be covered now. But besides that, it’s a denali, I shouldn’t be having a new engine at 40,530 miles. I am happy that there is an investigation but it needs to be widened because my truck was right before the new model rollout but I am having the same issues. If needed, I have all my receipts and information and will provide the service rep at hare. The reason why its at hare vs andy mohr is due to me catching them not fully servicing my truck and joy riding my camaro zl1 after an oil change before I went home for a funeral.

I purchased a 2018 GMC Sierra 1500 6. 2 denali new. I followed all service requirements including oil changes by gm dealerships. 2025 I noticed my truck power was decreasing. Than I started to hear knocking noses. I took it to a dealership for diagnosis but they couldn't identify anything. Finally it started to skip this is when a dealership diagnose it as being an issue with the active fuel management system. They said my lifters, camshaft, and various other parts was damaged and had to be replaced. Additionally, they said it was a recall on 6. 2 engines with the same identical issue but my year wasn't included. The cost to repair approximately 10,000. I really need your attention to this matter! September 10, 2025 my truck placed me and others in danger when it lose engine power. Also my engine light was on for the first time.

Transmission shutters when going over 50mph.

The contact owns a 2018 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed toward the residence, the accelerator pedal was depressed and traveled to the floorboard, and the vehicle failed to drive forward as intended. The vehicle started rolling backwards and the contact carefully maneuvered the vehicle while attempting to park. There was no warning light illuminated. The vehicle was towed to the dealer and diagnosed with transmission failure. The contact was informed that the transmission needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure. The failure mileage was approximately 101,000.

The contact owns a 2018 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle jerked abnormally hard. No warning lights were illuminated. The vehicle was taken to the dealer, where it was diagnosed with transmission failure. The contact was informed that the transmission needed to be replaced. The vehicle was repaired; however, the failure reoccurred. The vehicle was taken to the dealer, where it was diagnosed and determined that the transmission was failing. The contact was informed that the transmission needed to be replaced. The vehicle was not repaired. The contact was informed that the repair was not covered under warranty. The transmission was replaced two years ago. In addition, the contact stated that the original transmission had failed at 130,000 miles. The manufacturer was not made aware of the failure. The failure mileage of the second transmission was approximately 40,000.

Transmission shutting and torque converter came apart destroying the transmission.

I have a 6. 2 engine that had a number 4 cylinder failure due to a engine defect of the crankshaft. They have recalled the 6. 2 motors on the 2021-2024 year models. The 2018 year models with the 6. 2 engine should be recalled also bc they are having the same issue. Please help.

The contact owns a 2018 GMC Sierra 1500. The contact stated while driving approximately 70 mph and attempting the pass another vehicle, the accelerator pedal was depressed; however, the vehicle lost motive power and decelerated unintendedly. The contact pulled over and restarted the vehicle however, the vehicle failed to accelerate above 40 mph. The vehicle was later taken to the local dealer who diagnosed that the transmission was faulty and needed to be replaced. The vehicle was not repaired. The manufacturer was not yet contacted. The failure mileage was 81,000.

The contact owns a 2018 GMC Sierra 1500. The contact stated that while driving at 60 mph, there was an abnormal vibration coming from the steering wheel. No warning light was illuminated. A dealer was contacted. The vehicle was taken to the dealer, where it was diagnosed, and determined that the transmission needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure and transferred the contact to the NHTSA hotline to report the failure. The approximate failure mileage was 125,326.

I am the original owner of a 2018 GMC Sierra 1500 with the 6. 2l l86 engine and 8-speed 8l90 transmission. I began experiencing severe transmission shuddering and harsh shifting, especially at lower speeds or under light acceleration. When the issue occurs, I press the gas and the engine revs up to 6,000 rpm without reaching 20 mph, making it extremely difficult — and dangerous — to merge into traffic or cross intersections. This issue has worsened over time and is now a critical safety concern, especially with children in the vehicle. I have researched this issue and found that many owners report the same transmission defect, and there is an open class action lawsuit and a gm technical service bulletin (TSB #18-na-355) describing the exact symptoms. The vehicle has become unsafe to drive. GMC should issue a recall or mandatory repair program for this known defect before someone is injured or killed.

I own a $35,000 2018 GMC Sierra 1500 6. 2l v8 4x4 denali, which is currently down due to engine failure while I was driving down the road. . Never had a check engine light on the dash. Haven't had the truck a year before it quit. Rods knocking, crankshaft bearings, loss of power, high rpm with little acceleration. I could have the peddle down to the floor and would barely get to 20 mph. . The motor would jump so bad, you would think it's going to jump out the truck. I have replaced several parts on the truck, including oil pump, filter, solenoid valve sensor, fuel pump, injectors, and sensors, battery, starter a couple times. Did all that replacing for it to get worse and finally quit while driving. . I was stranded in the middle of the road. . Iv reported it to the recall people, but nothing helped. I have taken my vehicle to express Chevrolet and they did a diagnostic test, which I provided the list they gave me below. When I took it to them, I was using endurance warranty, but they denied my claim due to the issues and they didn't cover them. At the time, the motor was still jumping, but smoke was coming out the tailpipe extremely bad, the truck was jerking and jumping. After replacing everything I listed, the truck got worse, started screeching and knocking loudly, loss of engine power, little acceleration. The day the motor quit on me while driving, I got the mph up to about 55-60 and it just quit, and hasn't started back since.

Gm has discontinued a critical engine belt on the 2018 GMC Sierra 1500 5. 3l eassist. This makes the truck undrivable and unsafe to own, even though the vehicle is still under financing and only 7 years old. There is no available part, and no alternative has been offered by the manufacturer.

The transmission would purge forward when shifting gears. The shifting was very rough. This vehicle had recently been in accident.

Transmission just would not go them all of a sudden it jersey really hard in second gear an start to pick up speed. . Cold starts it change gear really hard in second gearc often times slipping then going into gear really violently. . Need fix ASAP dealer has service once with the issue, change fluid an stopped a while ago now issue is back an worst then before. . 44,785 vehicle should not operate this way. 4×4 awd trans starts at 6500 to replace an go up to about 13200 to replace.

When driving the transmission will shift hard almost jumping forward, especially from a stopped position into 1st.

I have taken it in due to engine mounts 4 different times, transmission replaced and in October 2024 I took it in for issues I was experiencing like I had before my transmission went out. I did not get my truck back until almost Dec 2024 and that was due to there employee backing into the front end of my truck. So after all that my warranty was up Dec 24 2024 and then on April 16th 2025 I was driving my 2018 GMC sierra 6. 2l 1500 denali 129,600 miles at approx 30 mph it was late so the streets were empty and we started to hear a knocking or what I thought at the time was a very bad exhaust leak. We parked and then we started to try to make it home very slowly which we did and it was not making to much noise. The next day I called GMC and explained they said bring it in. I towed it there to be safe but it did start and still ran at very slow speed. They called me and said that the lift side rockers/ lifters 1 failed and it was stuck due to a misfire and that the engine would need to be rebuilt and sent me over some very vague break down which looked like a lump sum price. I requested and better break down and got a screen shoot and that when he said that’s the best they can do. There were no engine lights on or warnings nothing at all. It also just got serviced at GMC for an oil change on February 27th 2025 along with some air filters. Today is April 29th and still waiting for the service manage to call and see if they can do anything to help out instead of charging full price. I will attach pictures of the cost break down if possible. Thank you.

When I first bought my 2018 GMC sierra with the 8 speed transmission it would shift hard from first to second gear. Then at around 58,000 miles my truck also started to have a vibration coming through the steering wheel around 45-55 mph. I took it to the dealership and they changed the transmission fluid and did a software update. I am now at 80,000 miles and my truck still shifts hard from first to second gear and makes a grinding sound when accelerating sometimes. I am afraid to drive my any long distances for fear of the transmission malfunctioning. I have not been back to the dealership since my truck is no longer under warranty. So the problem has not been reconfirmed by a dealer or independent service center or inspected by the manufacturer. There have been no warning lamps or messages or other symptoms. I hope that gm is held accountable for putting a faulty 8 speed transmission in my truck.

My starter quit at 81,000 miles. It has always been a bit weak starting, but I have never had a starter go out on a vehicle at 81,000. I have replaced it, and the rebuilt starter is better than what was ever on this vehicle. I am also having problems with the transmission shuddering, shifting rough in low gear, and sometimes it reverses fast. Repair shops won't even touch the transmission. The dealership stated they couldn't get the problem to replicate the issues even though they know there are issues with the 8 speed transmissions.

Transmission malfunctioned while driving, causing no available power to move the vehicle. Had to coast in neutral and stopped in the road. Towed the truck to the dealer and they confirmed the transmission has failed. No warning lamps present or pre-indication of failure.

When accelerating (at times) truck will shudder. Sometimes barely noticeable, sometimes violently. Was told by dealership that torque converter is going out and will be $4000 to replace but may not even fix issue. Looking online, appears that many (1,000’s) people are having same issue and that there is even a class action lawsuit about this issue. But no investigation by nhsta yet, even though I can see many many complaints of similar issues.

The contact owns a 2018 GMC Sierra 1500. The contact stated while driving at an undisclosed speed, the engine temperature rose to 210 degrees and the vehicle started jerking. The contact stated that the failure also occurred while idling for a while, or while stopped at a traffic light while refueling, and before accelerating. The failure occurred once the engine temperature rose to 210 degrees. There were no warning lights illuminated. The vehicle was taken to a certified mechanic at a transmission shop who confirmed there was a failure with the transmission; however, the mechanic was unable to determine the cause of the failure. The dealer was contacted; however, the vehicle was not diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was 117,000.

The contact owns a 2018 GMC Sierra 1500. The contact stated that while driving at 45 mph, the vehicle began to shudder, and he decreased the speed. The contact drove to his residence. The next day the vehicle was driving as expected until it became hot and began to shudder again. The transmission was not shifting as designed. The contact checked underneath the vehicle but failed to locate an issue with the transmission. The rear differential was hot and burned his fingers, but medical attention was not provided. The vehicle was taken to the local dealer, where it was diagnosed that the torque converter and transmission needed to be replaced. The vehicle was not repaired. The manufacturer was contacted, but no additional assistance was provided. The failure mileage was approximately 22,000.

Vehicle jumps when shifting gears. When coming to a stop it jumps forward. Hard shifting.

The contact owns a 2018 GMC Sierra 1500. The contact stated that the vehicle began shaking while driving at approximately 28 -35 mph. There were no warning lights. The contact continued to drive cautiously. The vehicle was taken to the dealer who diagnosed that the torque converter had failed and needed to be replaced. The vehicle had not been repaired. The contact stated that it was the second time the torque convertor had been replaced. The first time was around 27,000. The manufacturer was made aware of the failure. The manufacturer had referred the contact to the NHTSA hotline to file a safety complaint. The failure mileage was 66,000.

Shaking when accelerating. Sometimes so extreme it feels like you have been hit by another car. Random, inconsistent, and comes out of nowhere.

Knocking, stalling, shaking, lost of power and steering problems. Serviced transmission twice and I was advised to serve every 30000 miles!!! I owned several types of vehicles but I never heard such things before. Technician told me that apparently many GMC customers reported same problems.

Engine lifters failed. Heard ticking noise first day truck was purchased that gradually got louder but was told by GMC service shop it was normal to hear the ticking noise. Also when cruise control is on and you are decending a hill the rpms raise and you lose engine compression this will cause your speed to drop to around 20 mph and has happened nunerous times. . As well when making a turn sometimes or just driving the vehicle turns off while in motion and you have to coast to the side of the road and turn the key off and back on to start driving agsin. . The loss of power is a complete blackout no dash. . No engine nothing. As result of the lifter issue the engine also hard shifts in and out of slow gears. . I have not driven my truck in about a year and still owe 22k on it. The issues with this vehicle are the same as the recalled 6. 3 v8 engines.

The contact owns a 2018 GMC Sierra 1500. The contact stated while shifted into reverse, there was a loud clunking sound coming from the vehicle and the vehicle failed to respond as intended. The contact attempted to shift to drive(d) and neutral(n) and then back to reverse(r) however, the failure persisted. The vehicle was towed to a dealer where it was diagnosed and determined that the transmission needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 92,288.

We purchased our 2018 GMC Sierra 1500 z71 brand new at fairway Buick GMC in las vegas, nv. Pretty much off the lot we noticed some hard shifting, but over the last year/around 60,000 miles it has become progressively worse. Come to find out gm is aware of a known defect in the transmission used in this make/model and several others by gm which causes hard shifting and jerking while upshifting and down shifting primarily between 1st and 2nd gear. This malfunction has caused the vehicle to activate "limp mode" which doesn't allow the vehicle to move out of 1st gear, while driving on the road, putting the safety of the occupants and others on the road at risk. This first happened in January 2024 while we were moving and towing a 6' u-haul trailer. Luckily we were within a few miles of our destination and made it there safely. Upon taking it to autonation Buick GMC, we were told they had seen this issue before and the only solution would be to replace the transmission and would cost roughly $6,000-$8,000, and that's with the generous 20% discount they were willing to offer. We opted to have the transmission flushed instead and it seemed to fix the problem temporarily. Then on 6/24/24 while decelerating and coming to a stop light it hard shifted from 2nd to 1st then the check engine light came on and limp mode was activated. It was 110 degrees on this day in las vegas when my husband was driving home from work, and again by the grace of god, he was only 5 minutes from home and made it there safely. However, what if this had occurred with our two young children in the vehicle and we were no where near home? we would have been stranded in dangerous conditions potentially putting our safety as risk. This known defect in gm transmissions is 100% a safety risk and this needs to be investigated and recalled immediately. There is an ongoing class action lawsuit against gm regarding this issue and I will be looking to get involved as well.

The contact owns a 2018 GMC Sierra 1500. The contact stated that while driving on various occasions at various speeds, the check engine warning light illuminated, and the vehicle shuddered. Additionally, the drive(d) on the instrument panel started blinking. The contact stated that the engine revved, and the vehicle went into safe mode and the vehicle failed to accelerate as intended. The vehicle was pulled over to the side of the road and restarted. The vehicle was taken to an independent mechanic where it was diagnosed and determined that the transmission needed to be replaced. The vehicle was currently being repaired. The manufacturer was notified of the failure. The failure mileage was approximately 40,000.