2018 GMC Sierra 1500 transmission problems

Filed Oct 9, 2026 · Transmission · WA

My 2018 GMC Sierra 1500 experienced significant transmission problems that began as rough, inconsistent shifting, hesitation, and abnormal transmission behavior before eventually progressing to complete transmission failure. These symptoms were present before the transmission's ultimate failure and while the vehicle was still within its warranty period. Unfortunately, during the COVID-19 pandemic, local dealership service departments faced significant staffing shortages and appointment backlogs, making timely diagnosis and repair extremely difficult. By the time the transmission failed completely, the vehicle had exceeded the warranty's 84-month time limitation but remained substantially below its mileage limitation. Despite the relatively low mileage, the earlier symptoms, and the extraordinary circumstances affecting service availability, General Motors declined to provide warranty or goodwill assistance. I was forced to bear the substantial financial burden of a major transmission failure in a vehicle that had not reached the mileage threshold established under its warranty. I believe this failure warrants investigation because transmission problems involving GM trucks and SUVs from this period have been widely reported by other owners. I am particularly concerned about whether GM was aware of recurring transmission defects, whether affected owners received adequate notification, and whether these failures present a potential safety risk through unexpected loss of propulsion, hesitation, or unpredictable shifting. I request that the federal safety agency review this complaint alongside similar reports involving 2018 GMC Sierra transmissions to determine whether a recurring defect exists and whether further investigation or corrective action is warranted.

Filed Sep 17, 2026 · Transmission · CA

Vehicle purchased Certified Pre-Owned in October of 2021 with roughly 43,000 miles. During the first service (47,598 miles) at a GM dealer I reported very hard shifts, but this issue was ignored during service. At the next servce (54,571 miles) I again reported the hard shifts and "surging" when coming to a stop but the dealer reported they were unable to replicate the issue and did not address it. At the next service (61,620 miles) I reported the issues with the transmission once again and this time they performed a transmission fluid flush/replacement, acknowledging the issue and asking me to drive for 200 miles and return if the issue was not fixed. I returned at 62,058 miles as the issue was not resolved and they replaced the torque converter. During my next visit (68,709 miles) I reported the issue was still present but was informed they would not address it as I was now outside of warranty. I reported this to GM but was told to pay for a diagnostic and repair and "hope" that the dealer would elect to cover it.

Filed Sep 16, 2026 · Suspension, Transmission · MS

Unknown

Filed Sep 6, 2026 · Engine, Transmission · KY

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.

Filed Sep 4, 2026 · Transmission · VA

Within the first 3 years of purchase as a new vehicle, my 2018 GMC Sierra Denali equipped with the GM 8L90 automatic transmission developed a pronounced judder during light acceleration, resembling driving over rumble strips. The condition was first reported to an authorized GMC dealer on October 23, 2021, at 26,648 miles while the powertrain warranty was in effect. GM authorized a transmission-fluid exchange from the technical service bulletin (TSB) 18-NA-355, dated April 2020, but that repair did not provide a lasting correction. The condition continued, and in 2026 the authorized dealer diagnosed an “internal stator issue causing judder on light acceleration” and recommended replacement of the torque converter. We completed the repair and retained the removed converter. The defect affected the vehicle while accelerating and created concern about predictable power delivery when merging, entering traffic or crossing an intersection. Continued torque-converter malfunction can generate heat and debris, damage the transmission and potentially impair acceleration or power transfer. GM had issued technical bulletins addressing torque-converter shudder in 2018 Sierra vehicles before this truck was purchased, but there has been no recall. I request that the federal safety agency evaluate whether this recurring defect presents an unreasonable safety risk in GM vehicles equipped with the 8L90 transmission.

Filed Sep 1, 2026 · Transmission · NY

Automatic Transmission not shifting properly unable to accelerate bangs gears while shifting noises from the transmission not reported no warning lamps

Filed Jun 11, 2026 · Engine, Transmission · AR

Vehicle Details: 2018 GMC Sierra 1500 Z72 4x4, 5.3L V8 EcoTec3 engine, VIN: [XXX] Mileage at time of incident: 220,000 miles Location: [e.g., Little Rock, Arkansas area or specific road/highway – please provide if desired] What happened: The 5.3L V8 engine’s hydraulic roller lifters failed. One or more lifters collapsed, stuck, or lost proper oil pressure/operation. This led to improper valvetrain function, causing loud ticking/knocking noises, cylinder misfires, significant loss of engine power and performance, and internal engine damage (such as camshaft lobe wear or related components). Component or system that failed or malfunctioned: Hydraulic valve lifters (camshaft followers) in the engine valvetrain, associated with the Active Fuel Management (AFM) system. The failed lifter(s) and related components are available for inspection upon request. How safety was put at risk: The engine malfunction resulted in sudden or progressive power loss and misfiring while driving. This reduced the vehicle’s ability to accelerate or maintain speed, especially in traffic or on highways, creating a hazardous situation that put my safety and the safety of other road users at risk of collision or breakdown. No accident or injuries occurred , or other symptoms prior to the failure with details recall, e.g., ticking noise timeline, misfires Has the problem been reproduced or confirmed by a dealer or independent service center? “Yes, confirmed by shop inspection” Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others? [Yes] Additional notes: Repair estimate is approximately $20,000 (likely due to extent of internal damage requiring major engine work or replacement). This failure aligns with a well-documented issue in GM 5.3L engines equipped with AFM. Vehicle status parked INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed May 15, 2026 · Suspension, Transmission · WA

The transmission has always been rough. It has now gone out at 75,000 miles. This transmission issue really seemed to get worse about 50,000 miles. But when I called the dealer, they said they were backed up and couldn't get to it for 9-12 weeks (Covid excuses at that point). Then, it really had an issue going down a large grade into [XXX] . But the issues seemed fairly intermittent. I had an independent shop who said it was hard to tell if it was intermittent. They didn't find metal shavings at the time. ADDITIONALLY, it has also always been a little rough driving. A mechanic looking at it today told me there are no sway bar links at all. This truck has not been modified. This had to have come off the line faulty. Among all the other things. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Feb 28, 2026 · Transmission · SD

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.

Filed Feb 20, 2026 · Transmission · 130,000 miles · LA

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.