*Median odometer reading when the problem happened, where owners gave one. One complaint can name several problem areas.
Structure › Body
At approximately 9,000 miles and 9 months of ownership, both front wheelhouse liners on my 2025 GMC Sierra 3500HD Denali Ultimate permanently deformed and sagged into the front tire clearance area. The truck is completely stock, including the factory wheels, tires, suspension, and ride height. No modifications have been made that would affect tire-to-wheelhouse clearance. The condition occurred during approximately four hours of highway towing at approximately 65 MPH while pulling a travel trailer weighing approximately 12,000 pounds. Ambient temperature was approximately 105 - 114°F and side winds were approximately 20 MPH. Both front wheelhouse liners became visibly deformed and sagged…
Aug 27, 2026Service brakes
The electronic part of the truck gave a warning and shut off my trailer brake system while towing a 21K 5th wheel trailer (X2). The truck is available for inspection. Any part of the electronics package that has the ability to disable a trailer braking system while towing needs to be removed/disabled immediately. The truck has not been seen by a dealer yet. yes there was a warning I briefly saw both times, but I can't say what it said.
Apr 17, 2026Equipment
The contact owns a 2025 GMC Sierra 3500 used for hauling a 2026 Aluminum Trailer equipped with a DeeMaxx: DBI-7K-MAXX-SS-KIT brake kit. The contact stated that while driving at an undisclosed speed, the brake caliper bracket detached due to insufficient generic quality bolts included in the brake kit. The contact pulled over and had the trailer towed to an RV park. The vehicle was not diagnosed or repaired by an independent mechanic or dealer. The manufacturer was made aware of the failure but informed the contact that the failure was caused by improper installation. The failure mileage was unknown. The VIN was not available.
Apr 10, 2026Power train
The contact owns a 2025 GMC Sierra 3500. The contact stated that the transmission was shifting hard and was jerking while shifting gear. Additionally, the vehicle failed to accelerate above 50 MPH. The messages âReduced Accelerationâ and âDEF Lowâ were displayed. While refueling the vehicle, the fuel gauge failed to correctly display the level of fuel inside the fuel tank until the vehicle had been driven for approximately 20 minutes. The vehicle was taken to the dealer to be diagnosed, and the contact was informed that the transmission needed to be updated. The system was recalibrated; however, the failure persisted. The vehicle was taken to another dealer, George Kell Motors (3808…
Mar 1, 2025 · 40,000 milesTires › Sidewall
I am reporting a potential safety defect involving Goodyear Wrangler TrailRunner AT tires size LT275/65R20. I purchased a new 2025 GMC Sierra 3500HD in August 2025. By the time the vehicle reached approximately 1,800 miles, noticeable sidewall bulges appeared on both rear tires. As a 36-year automotive professional, I recognized the serious safety risk posed by this condition and replaced all four tires at my own expense with a different brand. Since then, I have seen multiple reports of similar sidewall failures on brand-new trucks, which suggests this may be a systemic issue. Based on my experience and these reports, I believe this defect may be known to both Goodyear and GM but has not…
Oct 15, 2025Electrical system
Randomly when the truck is turned on, the turn signals will stop working, no noise, nothing. When this happens, the infotainment system also stops working. It is unsafe to be driving and not knowing if your signals are working or not. This has been happening since the truck was purchased from the dealer.
Mar 6, 2026Service brakes
The truck automatically engages the parking brake ONLY when on an incline, never at any other time. I am so used to engaging the parking brake at all other times I also engage it when on an incline. The problem is the truck DISENGAGES the brake automatically after I've engaged it. This has happened multiple times when I've been towing a large boat on a launch ramp or towing my heavy 5th wheel. I can be fully exited from the truck and 10 ft away when it disengages and I watch it lurch forward. Simple answer would be for me to not engage the brake on an incline, but its a total habit all the time so I never remember to not engage it on an incline. This is a dangerous feature that needs to be…
Jan 30, 2026Engine
Oil cooler for truck is defective and thus allowed all oil to be mixed with the coolant. GM is stating they will flush engine and replace with exact same part. Very common issue and sad to have a $100k truck and it is junk.
Dec 20, 2025
Owner complaints are submitted to NHTSA by the public and are not verified. Shown as filed (NHTSA removes personal details); long reports are shortened.