driving approximately 50 mph when vehicle suddenly made loud bang and locked up rear brakes for 25' coming to a stop in road side ditch, numerous vehicles had to make evasive actions to avoid me and other vehicles. flat spotted tire abut no visible physical damage. sat on side of road for transmission temp to cool down then drove to shop without repeat. called dealer was told the earliest appt was a month away. have not been able to repeat incident so far. this has happened a few times and is becoming more frequent, mfg has tsb issued but indicates they cant assist because my warranty has expired so i will have to pay 225 per hour diagnostic fee. this is untenable and dangerous. this needs a recall and repair ASAP.

- Atlantic, IA, USA

driving 45 mph westbound i70 at eisenhower tunnel, vefhicle made loud bang, brakes locked up momentarily slowing vehicle to around 25mph. multiple vehicles had to make evasive manuevers to avoid collision. vehicle released after a 15FT skid. pulled over to safety and inspect for damage, tires were falt spotted but no damage was visible. called dealer servcei and was told to make appt and set for diagnostic. service could not replicate or find damage so I was sent on my way and told if it does it again let us know. I am scared to drive this vehicle its unsafe

- Atlantic, IA, USA

driving 65mph when vehicle attempted to downshift itself for no reason when instead the rear axles locked up and made a massively loud bang as if axle fell off, let off gas, smoke pouring from rear tires, skidded about 8 feet, it released then locked up 2 more times within 30 secs before I could get off road out of traffic flow. mfd has a tsb for this issue(#21-NA-275 GM) not sure if its transmission or braking system Dealer service could not replicate and told me it was probably my trailer(wasnt traveling with trailer) no warnings, no codes occurred initially at 56000 mile, has happened 10 or 12 times since then. very scary, im afraid to drive or tow now that dealer mentioned trailer brakes.

- Atlantic, IA, USA

I was driving approximately 60mph pulling a trailer when the back tires locked up for approximately 2 seconds. This happened 3 times within 30 minutes. I've taken it to the GM repair shop. They have seen this happen to 3 or 4 vehicles. Due to not being able to replicate the fault it has been difficult to diagnose. They are going to replace the transmission valve body hoping that will take care of the issue. This is extremely dangerous to everyone on the road when this happens. There are many forums out there that I've read and have been close to deadly accidents involving cars, trucks, RV's, and semis as they've ran off the roads. This seems to be something worth looking into and ensuring GM puts out a recall for. In my case, I am going through an extended warrant for my 2020 3500 with 112,000 miles. The warranty company wants the GM technician to replicate the fault... which isn't possible without hooking up a trailer... also very dangerous which I refuse to do until the issue if resolved. In any case, I will have to hook up a trailer once the part is replaced... praying that it won't happen again.

- Fountain, CO, USA

The contact owns a 2020 GMC Sierra 3500. The contact stated that after stopping at a stop light, the light turned green and the contact depressed the accelerator pedal however, the vehicle failed to accelerate as intended. The contact drove a short distance and noticed that the failure was reoccurring. The contact drove the vehicle to a safe location and turned off the vehicle. The contact exited the vehicle and noticed that the exterior of the vehicle was covered with transmission fluid. The contact stated that the transmission fluid was also on the undercarriage of the vehicle and on the ground. The vehicle was towed to the dealer where it was diagnosed with a failed transmission fluid line. The contact was informed that the transmission fluid line needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and advised the contact to report the failure to the NHTSA Hotline. The failure mileage was approximately 28,000.

- Lincolnville, ME, USA

While accelerating from about 45 - 60mph the truck made a loud bag and the rear tires locked up causing the vehicle to skid. This happened 4 times and nearly caused the cars behind me to crash.

- Evans, CO, USA

Rear tires locking up out of no where almost made me jack knife.

- Dalbo, MN, USA

The exhaust system is directed to the rear of the vehicle and when towing causes extreme heat to build on the item being towed, in my case a 5th wheel camper. The heat has melted the trim on my camper and is a potential fire hazard.

- The Villages, FL, USA

The computer lite up the dash and reduced power, plus took the trailer brakes off line. This happened while loaded. To reset the system you have to pull over and turn the vehicle off. This happens 2-3 times per day. This was a problem at 600 miles. The transmission shifted from 10 gear to 5th gear while driving 75 miles per hour. The truck had 75,000 miles on it. Had to send another truck out to pick up the load in Santa Rosa New Mexico. The dealer Glenn Polk in Sanger has been working on for the last 4 months There is never a warning until the lights come on with a system failure.

- Irving, TX, USA