2020 GMC SIERRA 1500 Complaints

I am reporting an ongoing safety issue with my 2020 GMC Sierra 2.7L related to the transmission. On two separate occasions within the same month, my truck broke down in the middle of the street, requiring it to be towed to the dealership for service. The first time, the dealer informed me they repaired a part inside the transmission and stated the truck was fixed. However, after picking up the vehicle, the issue persisted, though not as frequently. When I called them, they advised me to drive it for another 100 miles so the valve could fill with oil and the transmission could properly recalibrate. After a few days of driving, the same issue occurred again — the truck stalled in the middle of the street, and I had to have it towed once more to the dealership. This time, the truck remained at the dealer for about a week. They replaced another part inside the transmission and returned the truck to me, noting that it only had about 40 miles of warranty remaining. I asked the dealership to extend the warranty or give me at least two months to test the truck and confirm the issue was resolved, as I am genuinely concerned for my safety and my family’s safety if the vehicle breaks down again on the road. They told me they would respond within two days, but it has now been over 10 days with no response. I am currently afraid to drive the vehicle because of the risk of it breaking down again, especially with my family inside. I am requesting that NHTSA review this issue for potential safety concerns with the transmission system in this vehicle model.

Lifter failure at around 102-103k miles, was doing a random misfire and transmission studder ( due to the dfm system activating, cutting down cylinders to save fuel while driving, this was happening since approx 59k miles, dealership and gm was aware of it and they said it was normal, but that normal misfire turned into a failed lifter causing misfire and studder. I ended up replacing the lifters myself put solid lifters and a new camshaft that would eliminate the dfm system and studder, ran good no studder and random misfire, and now my crankshaft or oil pump is bad which I will remove motor to furthermore inspect. I’ve read forums and stuff where people would get a lifter job done and then soon after couple thousand miles later the motor goes bad. The 5.3 motors have bad crankshafts, oil pump and lifters just like the 6.2lt motors. After the lifter and cam repair, it ran good for couple thousand miles shortly after My gmc threw an “oil pressure low turn off vehicle code”, turned off vehicle immediately and checked oil, verified oil was good. Gm will not cover it because of it being way out of warrenty when I had issues with random misfire around approx 70-78k miles, and to note that my cat converter went back when lifter failed aswell. Also to note that when the lifters fails it throws a speed reduced to 55 mph, traction off, steering assist reduced, and brakes reduced, this is a safety hazard and also it will drain the battery and cannot start it if you pull over on the side of the road and turned it off and on again to make it back home.

TRANSMISSION SHURTTING, JERKS, AND VIBRATION, BAD TORQUE CONVERTER BUBBLE AND PELLING PAINT. IT FEEL LIKES ENGINE IS LOSSING POWER

My 5.3 engine spun a bearing on the crank. Same exact problem the 6.2 got recalled for. Now if I put a used engine in it’ll cost me around $6,000.

6.2 liter engine fail- replaced at new cost, 20,000 miles later another 6.2 engine failed. unable to get new engine due to GMC finally recalling the engine. My VIN is not included in the recall. I now have no vehicle to drive but still have a loan to pay.

Driving at freeway at 65mph, suddenly is air noise like air conditioning blows air at high fan speed, than the dash info shows (Engine Power is Reduce) try to accelerate to pull out of lanes, and it did not, keep losing speed, as slowly move lanes to the right of freeway, and then exit.. This is the second time of this incident, first time under warranty, dealer fix transmission first time, then two months later, the tansmission was replace wit a newone, now is passed warranty, had the car taken to dealer, they gave me and estimate of more then $10,000 to fix the vehicle, this happen on May 21, 2025...

Transmission valve control system malfunctioned, causing rear wheels to lock up at high speeds, in turn causing tires to skid out. This issue almost caused me to loose control of the vehicle, potentially endangering the safety of myself and others near me at the time. This is the second time this has happened while I have been driving this vehicle. There was a recall related to this issue, which was addressed, but very clearly did absolutely nothing to prevent this incident from occurring.

Transmission valve control malfunctioned, causing rear wheels to temporarily lock, skidding the tires. This almost caused me to loose control, endangering myself and others around me. This is the second time this problem has happened. A recall related to this was addressed on this truck, though it has clearly done nothing to prevent it from happening.

Engine Light came on, performance rough at various speeds / conditions, and smelled like burning and strong urea smell. GM Maintenance identified a failed DEF injector / replaced

Engine light would come on for a few days and than turn itself off. this occurred for about 8/9 months; however, instructed by the GM Maintenance department that if the vehicle came in and the light turned off before they got to it i would be charged for the diagnosis and no work would be performed. Engine light came on and i was able to park the vehicle / they picked it up and read it prior to putting in their lot until a tech became available. GM Maintenance was able to diagnosis that there was an issue with the EGR sensor and NOx catalytic converter without filter failed / both items replaced