My truck has been exhibiting hard downshifting at certain speeds, when the powertrain loads up such as a grade change, and requires a downshift. I have complained about this issue to the dealership as early as 2022, and 33,185 miles. The dealership made me pay for a transmission $388.90 flush which did not resolve the issue. The problem has become progressively worse, to the point where the toll road transponder fell of my windshield during a recent harsh downshifting incident. At the same time there was an existing MIL and derating for a DEF heater and NOx sensor failure, so during a warranty visit I asked that this transmission issue be addressed. On Friday March 13, the dealership called and said they confirmed the hard downshifting, albeit not as extreme as I described. The technician said that the valvebody needs to be replaced. At the same time, they performed a TCM flash for the 10L1000 momentary wheel lockup recall. The dealership then said they could not get the truck to set a P0747 code, said that GM refuses to replace the faulty valve body, and recommended I take the vehicle home unrepaired, and to come back when the P0747 code is set. I requested they continue to drive the vehicle. Today March 20 the dealership called and said they could not get the code to set, and that I need to drive the truck and come back when the code appears, despite the truck exhibiting clear symptoms of a progressively wearing feed limit low valve. N242454441 does NOT seem to indicate a P0747 code is required to replace the valve body. This vehicle is not safe for towing a 20,000+lbs and GMC is refusing to repair a transmission with symptoms congruent with N242454441. The dealership still has possession of the vehicle and wants $360+ in diagnostic labor.
2020 GMC Sierra 3500 transmission problems
19 complaints (37% of all complaints for this car). 3 crashes reported.
- owner complaints
- 19
- of this car's complaints
- 37%
- crashes
- 3
- recalls
- 2
Which part fails
Owners did not name a specific part.
At what mileage
Complaints by mileage at the time of the problem.
GMC Sierra 3500 transmission problems in other years
Related recalls
Power train: automatic transmission: fluid/lubricant: valves/valve body
- What is wrong
- General Motors, LLC is recalling certain 2020 Chevrolet Silverado 2500, 3500, GMC Sierra 2500, 3500, and 2020-2022 Chevrolet Silverado 1500 and GMC Sierra 1500 vehicles that may have been repaired incorrectly under recall 24V797. The transmission control valve may fail and cause the rear wheels to lock up.
- Risk
- Rear wheel lock up increases the risk of a crash.
- Remedy
- Dealers will inspect the vehicles and update the transmission control software, free of charge. Owner notification letters were mailed March 6, 2026. Owners may contact GMC customer service at 1‑800‑462‑8782 or Chevrolet customer service at 1‑800‑222‑1020. GM's number for this recall is N252516560. Vehicle Identification Numbers (VINs) involved in this recall became searchable on on February 12, 2026.
Recall number 26V083000 · Recall details
Power train: automatic transmission: fluid/lubricant: valves/valve body
- What is wrong
- General Motors, LLC (GM) is recalling certain 2020-2022 Chevrolet Silverado 1500, 2500, 3500, GMC Sierra 1500, 2500, 3500, 2021 Cadillac Escalade, Escalade ESV, Chevrolet Tahoe, Suburban, GMC Yukon, and Yukon XL vehicles equipped with diesel engines. The transmission control valve may fail and cause the rear wheels to lock-up.
- Risk
- Rear wheel lock-up can increase the risk of a crash.
- Remedy
- Dealers will install new transmission control module software, free of charge. GM will provide a special coverage program to cover the repair of transmissions that are identified by the remedy software as containing a defective control valve. Owner notification letters were mailed December 12, 2024. Owners may contact GM customer service at 1‑888‑988‑7267, Cadillac customer service at 1‑800‑458‑8006, GMC customer service at GMC 1‑800‑462‑8782 or Chevrolet customer service at 1‑800‑222‑1020. GM's number for this recall is N242454440.
Recall number 24V797000 · Recall details
What 2020 GMC Sierra 3500 owners say
Most recent owner complaints, unedited.
The contact owns a 2020 GMC Sierra 3500. The contact stated that while driving at an undisclosed speed, the vehicle inadvertently went into LIMP Mode. There was no warning light illuminated. The vehicle was taken to the dealer, where it was diagnosed that the transmission valve body sensor had failed and needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and referred the contact to the federal safety agency Hotline for assistance. The approximate failure mileage was 130,000.
The contact owns a 2020 GMC Sierra 3500. The contact stated that while driving at 60 MPH, the rear differential seized, in addition, the contact was hauling a median size tracker on top of a flat bed. The flat bed jackknifed and hit the left side of the contact's vehicle. The vehicle was able to come to a stop. The air bags did not deploy. There was no warning light illuminated. A police report was filed. There were no injuries sustained. The vehicle was towed to a towing yard. The trailer was towed to the residence. The tractor was damaged in the accident. The vehicle was diagnosed by an independent mechanic. The contact was informed that the transmission had failed. The vehicle was not repaired. The insurance company was contacted. A claim was filed with the insurance company, and it was canceled a few days later by the insurance company. The manufacturer was not notified of the failure. The failure mileage was approximately 108,000.
Valve body failed while pulling my camper down the interstate. Transmission began to have issues and locked up on us while driving. Luckily i was able to avoid any accidents. Had truck towed to a private Transmission shop to have the transmission repaired. Shop advised the failure was due to the faulty valve body.
Greetings. In December 2024, I brought my vehicle in for the rear end lock up recall. The recall reprogrammed the transmission control module. As admitted, by yourself and GM this doesn't fix the problem. In addition, if the lockup occurs and a new valve body is required, GM is on back order with no date for delivery. Also, it is replacing it with the same valve body, i.e. you will have the same problem in the future. Nextgen Drivetrain has a valve body for around $1000 that fixes the problem. [XXX] . Please read the attached blog from Nextgen, they explain in detail, the problems and the fixes. I am scared to death to pull my travel trailer out of state with this looming problem. Please give us a better solution. Thank you. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
The contact owns a 2020 GMC Sierra 3500. The contact received notification of the federal safety agency Campaign Number: 24V797000 (Power Train); however, the part to do the recall repair was not yet available. The contact was concerned about the remedy repair not being adequate to repair the vehicle. The local dealer was contacted. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The manufacturer was made aware of the issue. The contact had not experienced a failure. Parts distribution disconnect.
Engine Coolant Low error constantly appears. GM Service provider states that engine coolant level is fine, but sensor may be defective.
Contacted General Motors to have the Recall software patch installed, appoint was set, vehicle was dropped off and now they are telling me there is nothing they can do, that the recall is not available. The software update is available, and is being installed on other vehicles. This is a life safety issue as the rear wheels can lock up at any time which could cause a vehicle accident involving the vehicle under recall as well any vehicles on the road around this vehicle when it happens. General Motors should be taking care of this asap instead of waiting. I do not feel safe driving the vehicle until they feel like they installing it.
I have a complaint about the recall response from both nasal and gm. I feel the cure is substandard. Why not just put new transmission control modules in to correct this problem. Very disappointed
driving 65mph on interstate, attempted to change lanes to pass slower vehicle and pressed upon accelerator pedal...truck violently skidded to a stop and sent me onto shoulder, many vehicles behind me swerved to avoid my vehicle. GM wont repair and says since they cant replicate its not really happening. this has happened twice in last 2 weeks.
Questions about the 2020 GMC Sierra 3500 transmission
Does the 2020 GMC Sierra 3500 have transmission problems?
Owners have filed 19 complaints about the transmission of the 2020 GMC Sierra 3500, 37% of all its complaints, more than any other problem.
At what mileage do 2020 GMC Sierra 3500 transmission problems start?
Not enough complaints include the mileage to tell.
Was there a recall on the 2020 GMC Sierra 3500 transmission?
Yes, 2 recalls: 26V083000, 24V797000. Check your VIN to see if your car still needs the free repair.
What year does the GMC Sierra 3500 have bad transmission?
The GMC Sierra 3500 model years with the most transmission complaints are 2020 (19 complaints), 2023 (14 complaints) and 2024 (13 complaints).
Other 2020 GMC Sierra 3500 problems
Electrical 9Brakes 7Engine 7Fuel system 6Body 5Tires 4Driver assistance 2Visibility 2Airbags 1Lights 1Locks 1Steering 1Wheels 1
VIN decoder
See the problems and recalls for an exact car
Buying a used 2020 GMC Sierra 3500?
Check the exact car before you pay: accidents, salvage or flood titles, odometer readings and previous owners.
Check its history