Complaint volume
290 consumer-submitted complaints are matched to this model year. Treat the count as a research signal, then read the actual summaries for repeated symptoms.
Complaint records
2018 GMC Sierra Complaints
290 consumer-submitted complaints on record for the 2018 GMC Sierra, grouped by component category.
290 Total complaints
10 Crash reports
1 Fire reports
5 Injury reports
Complaint data reflects consumer-submitted reports. A complaint is not proof
of a defect, recall, or manufacturer fault. Enriched severity fields come
from official bulk records when the complaint can be matched by ODI number.
Buyer interpretation
How to use these complaints before buying
Complaint records are most useful when they turn into inspection points, seller questions, and comparison checks against nearby model years.
Pattern to inspect
The most common categories are power train, engine, service brakes. Use those categories as a test-drive checklist instead of judging the vehicle from the total count alone.
Severity flags
Enriched records include 10 crash reports, 1 fire report, 5 injury reports, and 0 fatality reports. These fields come from complaint records and should be read in context.
Mileage clue
Mileage is available on 121 complaints, with an average reported failure mileage of 45,272 miles. Compare that with the mileage on the listing.
Questions to ask the seller
- Have you had any problems related to power train, engine, service brakes?
- Can I see recent maintenance and repair records?
- Has the vehicle ever been towed, involved in a crash, or repaired for the same issue twice?
- Can we also check the recall record for this 2018 GMC Sierra?
Used-car checklist
Use these complaints before the test drive.
Build a buyer checklist to turn these issues into questions and inspection points.
2018 GMC Sierra
Build buyer checklist Compare with other years Sends year, make, and model to pre-fill your checklist.
How severe are the 2018 GMC Sierra complaints?
10 Crash
1 Fire
5 Injury
0 Fatality
12 Towed
3 Medical attention
What are the most common 2018 GMC Sierra complaint categories?
POWER TRAIN 85
ENGINE 30
SERVICE BRAKES 15
UNKNOWN OR OTHER 14
ELECTRICAL SYSTEM 11
ELECTRICAL SYSTEM,SERVICE BRAKES 10
POWER TRAIN,ENGINE 10
STEERING 10
AIR BAGS 6
SEAT BELTS 4
290 total complaints on record
Latest complaints
| Date | Component | Summary | Severity | Mileage |
|---|---|---|---|---|
| Nov 2022 | FUEL/PROPULSION SYSTEM | Gas leak. My 2018 gmc sierra 1500 has been giving me two codes for evap leak small and large and i notice a black spot on my drive way under the gas tank wich in fact was gas. I can see the gas tank is wet but it comes from the top part of the gas tank. I been looking for recalls on this but there isnt any for this specific year of GMC sierra 1500 slt. | Crash: No Fire: No | Unknown |
| Nov 2022 | SUSPENSION,POWER TRAIN,TIRES | The contact owns a 2018 GMC Sierra 1500. The contact stated that while driving at an undetermined speed, the vehicle was shaking while shifting gears. The contact stated while shifting from four cylinders to eight cylinders, the rear-end was shaking violently. The hood latch warning light was illuminated. The vehicle was taken to the local dealer where it was diagnosed and determined that the tires needed to be replaced. The tires were replaced three times however, the failure persisted. The manufacturer was not contacted. The failure mileage was approximately 50,000. | Crash: No Fire: No | 50,000 |
| Oct 2022 | SERVICE BRAKES | Breaks are not working | Crash: No Fire: No | Unknown |
| Oct 2022 | STEERING | The contact owns a 2018 GMC Sierra 1500. The contact stated that while pulling up to park the vehicle at approximately 2 MPH, the power steering failed causing the contact to use an excessive an extra amount of effort while maneuvering the steering wheel to park the vehicle. The power steering assist warning light was illuminated. The contact took the vehicle to the dealer to be diagnosed. The contact was informed that the steering assembly and steering gear needed to be replaced. The vehicle was repaired. The manufacturer was made aware of the failure and filed a case. The approximate failure mileage was 39,000. | Crash: No Fire: No | 39,000 |
| Sep 2022 | POWER TRAIN | Experienced heavy vibration or shudder through transmission once fluid got to around 145 degrees. Also transmission has rough shift on the first shift of a drive cycle. When I started to research I found many of the same issues reported with 8 speed transmissions. I’ve also read about the issues with the lifters not working for the active fuel management system though I haven’t experienced that yet. The replaced my transmission fluid at the dealership under the powertrain warranty. This issue showed up at around 35,000 miles, so I am very worried about the safety and reliability of this engine and transmission. | Crash: No Fire: No | Unknown |
| Sep 2022 | UNKNOWN OR OTHER | In short, the moonroof of my vehicle spontaneously exploded into a million pieces one morning while driving. | Crash: No Fire: No | Unknown |
| Sep 2022 | ELECTRICAL SYSTEM,SERVICE BRAKES,ENGINE | While driving 35 miles per hour in the early morning hours I came to a 4-way intersection and applied the brakes slowly. Suddenly, I lost all power in the brakes and the steering wheel locked up. The lights, and stereo remained on, and my dash board display immediately showed a red check engine light. I immediately turn on my hazard lights, turned the ignition key off and tried to restart the truck. There was no clicking sounds. The truck would not start but the lights dimmed and the dash display now showed an intermittent yellow, flickering check engine light. After roughly 30 minutes while waiting for AAA to arrive I tried the ignition key and the truck started up with a red check engine light. Rather than attempting to drive I had AAA tow my vehicle to the Chevrolet dealership where I purchased the truck. | Crash: No Fire: No | Unknown |
| Sep 2022 | STEERING,SUSPENSION | My truck has a severe vibration or shake extremely bad at 60mph and up.i have tried new tires, front end alignment, and several different shops have told me they don't know what it is drive shaft or axels | Crash: No Fire: No | Unknown |
| Sep 2022 | UNKNOWN OR OTHER,SERVICE BRAKES | Received an error on the dash saying "Service Brake Assist". At the same time the brake pedal became very stiff and braking power was decreased significantly. I have received this same message and brake pedal stiffness with reduced braking power three times in the last 4 days. | Crash: No Fire: No | Unknown |
| Sep 2022 | UNKNOWN OR OTHER | Air conditioning condenser failed at about 48,000 miles. Seems to be a common problem that is a design defect. | Crash: No Fire: No | Unknown |
| Sep 2022 | POWER TRAIN | Transmission System, hard shifts and shaking causing vehicle to down shift hard and throw itself forward almost causing an accident when coming to a stop, when vehicle was taken into service they did not diagnose the vehicle for this problem, while driving vehicle shifted down so hard causing vehicle to be stuck in only 1st gear and would not shift out of 1st gear | Crash: No Fire: No | Unknown |
| Aug 2022 | SERVICE BRAKES | The service alert for the trailer brakes keeps going off constantly and continues to go off persistently almost making the vehicle undriveable. I was informed to file a complaint with your company by my local dealership as this is a recurring issue with GMC trucks. | Crash: No Fire: No | Unknown |
| Aug 2022 | SERVICE BRAKES | *A message and alarm kept going off on our truck "Service Trailer Brake". We are not towing a trailer, nor had we had a trailer hooked to this vehicle since 2019. It began only going off occasionally, but within a few weeks it was going off constantly. It would show repeatedly on the dash and the alarm would sound over and over. Trying to turn off the system was not successful, no matter how many times we hit dismiss. It was totally distracting and worrisome that something was wrong with our braking system in general. *The constant alarm and dash display made driving a very distracted experience. It is so loud that you cannot hear other outside noises. We were also concerned about the safety of our regular braking system. *I called the dealer where our truck is regularly serviced. They immediately said "Is it the Trailer Assist Alarm?," so it was obvious that this is happening to other owners regularly. It took several days to get in for an appointment. The shop mgr helped us to locate and pull the alarm fuse to stop the noise, so we could drive it to the dealership later in the week. The display was still going off when I pulled the truck into the dealership, as it has done all the way there (17miles from my home). *It was inspected by the GM dealership (Schwarz, INC. Honesdale, PA) and the defective switch was replaced at a cost to us of $127.14 on 08/11/2022. *This issue started several months ago (Feb 2022?), but it was a one time thing. So, we thought it was just a fluke. Then, a month or so ago it started again, but was happening only once or twice and would then disappear for days. Then, 2 weeks ago it began to happen continuously. | Crash: No Fire: No | Unknown |
| Aug 2022 | SERVICE BRAKES | I am getting a service alert for the Trailer Brake System. It is constant and loud and distracting and a significant safety hazard, not only because of the distraction, but also because it renders trailer brakes completely useless | Crash: No Fire: No | Unknown |
| Aug 2022 | VEHICLE SPEED CONTROL,ENGINE,FUEL/PROPULSION SYSTEM | THE SPEED OF THE TRUCK WILL NOT INCREASE. THE RPMS GOES REALLY HIGH AND THE TRUCK WILL NOT MOVE INTO THE NEXT GEAR. THE REAR END OF TRUCK VIBRATES. I TOOK THIS TO THE DEALER AND WAS TOLD IT IS THE TRANSMISSION FLUID IS FAULTY. THE CHECK ENGINE LIGHT DOES COME ON. I DID NOT HAVE THE NEW TRANSMISSION FLUID CHANGED BECAUSE DEALER SAID IS COST $300 FOR THE FLUID AND $100 FOR THE LABOR AND $168 FOR THE DIAGNOSTICS. SO I STILL HAVE THE SAME PROBLEM. ALSO TOLD YOU CAN NOT PURCHASE THIS TRANSMISSION FLUID NO WHERE BUT GMC. | Crash: No Fire: No | Unknown |
| Jul 2022 | UNKNOWN OR OTHER | Constantly getting “service trailer brakes system “ | Crash: No Fire: No | Unknown |
| Jul 2022 | ELECTRICAL SYSTEM,WHEELS,FORWARD COLLISION AVOIDANCE | The light in the dashboard gose dark and it gives me a warning collision alert and the tiers they spin out of control when turning or when I I’m driving I think it’s the tiers they have a lot of tread still… | Crash: No Fire: No | Unknown |
| Jun 2022 | ELECTRICAL SYSTEM,EQUIPMENT | Informant system and instrument clust/panel starts to change with nothing be clicked. Starts to phantom change everything which is deters from paying attention to actual driving becoming a safety hazard. Dealership has tried to update the software and still does not work. | Crash: No Fire: No | Unknown |
| Jun 2022 | POWER TRAIN | Transmission slams into gear in drive and reverse while driving it will slam into gear. And occasionally at speeds under 5 going up a hill it will have no power and struggle. I have 59000 miles on it last year around 53000 miles they did a transmission flush and that fixed it for about 9 months. Just took it back in they reprogrammed the transmission and it no longer slams In drive and reverse but still knocks back-and-forth while driving. | Crash: No Fire: No | Unknown |
| Jun 2022 | POWER TRAIN,ELECTRICAL SYSTEM,SERVICE BRAKES | I was stopped at a fast food drive thru and then I tried to go to the next window and the truck wouldn’t move at all it will just rev so I put it in parked turned off the truck and turn it back on put it on drive and was able to move for like 40 ft then it did it again so I had it towed to my home | Crash: No Fire: No | Unknown |
| Jun 2022 | ELECTRICAL SYSTEM,SERVICE BRAKES | Trailer brake modulator on 2018 GMC Sierra does not consistently signal trail brakes to work when needed on our 7,500 pound RV trailer. GMC dealer eventually found that the battery cables were undersized as installed with the factory towing package on the 2018 GMC Sierra. The undersized battery cables do not consistently deliver adequate voltage to the trailer brake modulator on the GMC Sierra, so inconsistent electric brake function for our 7,500 pound RV trailer. Dealer had difficulty diagnosing the problem as being the wrong factory-installed battery cables to go with the factory-installed trailer towing package. So it cost us $1,600 to have the GMC dealer correct a problem caused by the GMC factory installing undersized battery cables. Fortunately, this did not result in a collision for us, but it might for someone else. Our 2018 GMC Sierra kept sending vague, randomly timed warnings to the dashboard to "Check Trailer Wiring." Very frightening, dangerous and costly (for us) mistake by GMC. Will the brakes work this time, or fail on the way home? Problem started in 2021 RV season, but took awhile for us to recognize the need to take to the GMC dealer for them to diagnose base cause. Took time for us to experiment changing trailer wiring connector on bumper and trailer brake control on the dash. Work for awhile, then fail. Work for awhile, then fail. Arrrrgh! Ask GMC to put more adequate battery cables on ALL their vehicles, please. | Crash: No Fire: No | Unknown |
| Jun 2022 | POWER TRAIN | I have a 2018 GMC Sierra Denali. I started having problems with the 8-speed transmission at 18,000 miles. The vehicle has been to the dealership for a transmission fluid flush, a transmission relearn, a 5-week valve body replacement, two more trips to the dealership where the truck did not malfunction for them. I have had issues with an air leak on the driver side front door as well. That issue has not been resolved as well. I spent over $60,000 for the truck and have had nothing but problems. I have brought it to General Motors attention and all I would do is get a run around and no results. I was told that there is nothing more that they can do. I am beside myself and just sick as I do not know what to do. I bought a brand new vehicle in order to not have problems compared to a used one. | Crash: No Fire: No | Unknown |
| Jun 2022 | ELECTRICAL SYSTEM,SERVICE BRAKES | SERVICE TRAILER BRAKE SYSTEM - warning | Crash: No Fire: No | Unknown |
| May 2022 | UNKNOWN OR OTHER | The radiator developed a leak on the drivers side. This caused a loss in antifreeze. | Crash: No Fire: No | Unknown |
| May 2022 | POWER TRAIN,ENGINE | Leak detected in the engine oil cooling lines, requiring replacement. | Crash: No Fire: No | Unknown |