GMC Sierra 2500 harsh shifting problems

Filed Dec 8, 2025 · Transmission · MI

Pulling into a driveway and the truck made a loud clunk and the check engine light, traction control light, and a reduced engine power light came on and the truck came to an abrupt stop. When the gear shift was put into reverse or any forward gear the truck would rev up without touching the gas pedal. The left rear wheel locked up. After paying over $700 in tow bills to get the truck towed to our house and then to the dealer we were told that the transmission had a catastrophic internal failure. This truck only has 82,000 miles on it and is a 2021!

Filed Sep 1, 2025 · Brakes, Transmission · TX

Problem #1: Trailer brakes failed while pulling 40' fifth wheel trailer. Was driving at about 50MPH on a 55MPH road and was approaching a stop light. I went to apply my truck and trailer brakes simultaneously and quickly found out I had "lost" my trailer brake. This happened another two times within the next 10 mile trip to my house. I immediately disconnected my trailer and took my truck to the shop. The GMC Dealer fixed this issue, however, it is both scary and extremely dangerous to the public when something like this happens on a brand new truck. Problem #2: Right around 30,000 miles I was driving (unloaded) down the road at about 35MPH when I felt a hard clunk in the transmission followed by grinding noises - immediately a notice flashed on the dash stating the truck went into reduced acceleration and the check engine light came on. I brought my truck to a local GMC Dealer to be serviced on June 19th and they advised me it was the Allison transmission valve body. The part has been on back-order and my truck is still at the dealership sitting in the back lot with at least 4 other 2024 HD models. I called GM twice to inquire about Safety Recall N242454440 (covering 2020-2022 GM Vehicles) and recommend that it get extended beyond 2022 since the problem with the transmission valve body has not been resolved yet. I have not heard anything back from them since that call back in June.

Filed Jul 18, 2025 · Transmission · 68,000 miles · WI

The contact owns a 2024 Chevrolet Sierra 2500. The contact stated that while his son was driving 60-62 MPH in tenth gear, the transmission unexpectedly downshifted to seventh gear. There was an abnormally loud clunking sound coming from the vehicle. There were no warning lights illuminated. The vehicle was taken to the local dealer, where it was diagnosed and determined that the valve body needed to be replaced. The vehicle was not repaired due to the parts being on backorder. The manufacturer was contacted, but no additional assistance was provided. The failure mileage was approximately 68,000.

Filed Jul 9, 2025 · Transmission · GA

While driving the vehicle, I entered onto the interstate, as I accelerated into the flow of traffic, (approximately 45-50 mph) my truck suddenly and unexpectedly jerked and “clunked” extremely hard, I thought I had ran over a large object, approximately 5 seconds later it jerked and “popped” loudly. At that time the reduced engine power and check engine light came on causing my vehicle to suddenly slow down to 20 mph and almost being rear ended by a tractor trailer truck traveling the speed limit that had to hit his brakes e trebly hard to avoid a rear end collision. After removing my truck from the flow of traffic, I turned it off, exited the vehicle to see if I had ran over something, I did not. Cranked it up, no signs on the dash, as I started back to the travel lanes, it “surged & jerked” the reduced power and check engine light came back on. Once I got the truck to the dealership, the service manager informed me he knew exactly what it was, the transmission valve body was no longer good. He also informed me that my truck was now number 28 in line just at that dealership for the same issue and repair, then added that GM is out of stock on the parts and back order status.

Filed Mar 13, 2025 · Transmission · KY

Hard shifting. Back wheels locking up

Filed Sep 9, 2024 · Transmission · MI

2023 GMC Sierra Duramax Diesel with 10 speed Allison Transmission with 28,000 miles can't be driven. Currently at the dealership due to a transmission valve body problem, codes P0700 & P0747. While driving I felt a hard shift and the truck jerk. The engine light came on and my truck went into low power mode. Let it sit over night and truck would shift fine. This happened 3 times over a 1 month period. After getting to the Chevy dealer they told me the issue is with he valve body and said they have been having multiple trucks come in with the same problem. They have a truck in there since May (4 months!) They told me there is no ETA for the part. I've read this is a common issue happening on 2023 & 2024 trucks like mine. I've read that the problems have been going on for over 1 year. This is ridiculous for a $90,000.00 truck. GM should be putting new transmissions in them or buying the trucks back. I'm considering contacting an attorney to inquire about the lemon law or what other avenues I can take regarding getting the truck fixed, and fixed properly.

Filed Sep 26, 2023 · Transmission · TX

Shifting started to make a loud clunking sound. Then the vehicle wouldn't shift out of 3rd gear. The engine check light came on and the code determined it to be a faulty transmission control module (TCM). When looking at the TCM, I also noted that the TCM was very hot and the nearby cable cover had melted. When researching the issue, it was discovered that GMC Sierra 2500 and 3500, years 2009 - 2015 were having this same issue all over the continent. Resulting in a massive back order and leaving drivers stranded. There was no warning lights or sounds before my power train froze up.

Filed Oct 17, 2016 · Transmission · 106,191 miles · OR

Vehicle was exhibiting harsh shifting; upshifts/downshifts. Pulling into driveway from rural highway vehicle downshifted and passenger was thrown forward and almost hit the dash with her head, felt like it was shifting into park. Had vehicle towed to dealership. Vehicle would not shift into any gear for mechanic. Transmission repaired along with a wiring harness that prevented the main computer to communicate with the transmission. Reporting this because this is dangerous if this wiring harness fails as we could be out in the middle of nowhere with a vehicle that will not drive. Attaching invoice of repairs that show what parts were replaced by the dealer.

Filed May 21, 2015 · Transmission · 153,200 miles · OK

Slight clunking started when shifting into drive. Fluid on garage floor. Off to aamco. Found two holes in transfercase. The "4 star buffering ring" on shaft inside pounded two holes in casing. Just step on gas and torque pounds the ring into the casing until holes are made. All fluid pours out. Most people wont even know its happened until castastrophic failure. Several seals, chain, two gears, 3 bottles of fluid, "4 star buffer ring" and a new casing half was required. $2654.00 to repair for a 12 month warranty. Aamco pointed out I did nothing wrong. Its an engineered failure point by gm. Add this to ; #1-speedo gear failure-20mph and gage reads 90 MPH, #2-cd/radio burnt up, #3-water pump failure 16k miles, #4-cab of truck not attached to frame correctly "cab wobbling", #5-roof temp control unit failure, #6-passenger window motor stops working below 25 degrees, #7-factory installed battery was the wrong one when bought new in ogden, utah. Now,.... Airbags???

Filed May 18, 2013 · Body, Suspension · 134,000 miles · OH

I was making a right turn out of a parking lot and heard a load clunk. When I got home I was looking for the cause of the banging and found that the rear leaf spring shackle had rusted so bad it broke in half.