2018 GMC Sierra 1500 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 21, 2026 · Engine · GA

Customer states: thinks crankshaft pulley is loose due to prior water pump replacement-crackshaft pulley has nothing to do with water pump replacement. Before inspecting/starting engine verified oil level-oil level is on full mark. Started engine-loud rattling/knocking noise from engine-engine has internal failure-engine replacement is required. Also hearing noise in rearend-cannot test drive due to engine condition several tsb's on engine failures with 6.2l engines. Gm has possible recalls coming on 2019-2024 yr models. Not sure if earlier models maybe included underhood inspection 1 7003186 06ns 52.50 52.50 lbr-disc cust sat

Filed Sep 21, 2026 · Engine · CO

I was backing out of my garage and truck made strange noise and shut off . Tried to restart but just made ding and wouldn't turn over . Dash lights went blank. Had vehicle towed to shop and mechanic stated it was crank and connecting rods after he dropped the oil pan. I ordered new OEM engine and waiting on delivery . Been 5 weeks now since order . Vehicle only has 106,000 miles on it and have had it since 20,000 miles and all maintenance has always been done . Engine can be inspected at shop as new engine has not arrived

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 Aug 26, 2026 · Brakes, Electrical · IN

There was a mass recall on 2018 GMC Sierras to due to a faulty break pump vaccum. We are experiencing the same problems but for some reason were not included in the recall. We were told to reach out on here as others have to see what can be done as this is a saftety hazard.

Filed Aug 11, 2026 · Engine, Steering · NC

Head gasket failure and overheating. After fixed, power steering has just failed during driving. Will have to have it towed to shop