2024 GMC Terrain transmission problems

Filed Oct 21, 2026 · Transmission · 11,050 miles · MN

The contact owned 2024 GMC Terrain. The contact stated that while stopped, the gear shifter independently shifted from drive(D) to park(P). The contact turned off and restarted the vehicle several times and the vehicle operated normally. A dealer was contacted. The vehicle was taken to the dealer to be diagnosed, and it was determined that the transmission needed to be flushed because debris were found inside the transmission. The transmission was flushed and the vehicle was repaired. The manufacturer was notified of the failure and opened a case. The approximate failure mileage was 11,050.

Filed Oct 2, 2026 · Transmission · NV

GMC Adaptive learning transmission problems that lead to safety concerns, emissions reduction in MPG, and increased wear of the transmission. Regarding GM’s 9T45 automatic 9 speed transmission. Problem: - The GM Adaptive learning of the transmission does not have safe guards in place to prevent unsafe sift patterns and behavior. This results in shift flair behavior where the transmission will drop out of 3rd gear and pause before shifting to 4th gear. It will learn to lock out 9th gear and it will max out with 8th gear at freeway speeds reducing MPG. And it will fail to downshift appropriately while driving leading to the operator wondering why the vehicle will not accelerate when needed; this casual downshift delay then results in excessive downshifting to the lowest possible gear where the vehicle will then lurch forwards; and then it will pause and maintain said lower gear and continue accelerating for 1-2 seconds while the operator presses the brake pedal in response of the vehicle jumping forwards. Individual situations: 1) Lack of 9th gear use at freeway speeds. This is reducing the advertised emissions based on EPA testing. This behavior skews official EPA test results because vehicle operation is not as advertised. 2) Shift flair and unsafe shift delays. This is the most serious behavior. It leads to pauses and delays in acceleration of up to 5 seconds, and it leads to pauses and delays where the vehicle continues to accelerate up to 3 seconds after letting off the accelerator and pressing the brake. 3) Excessive wear. The badly learned behavior is causing issues with shift control pressure and logic, excessive clutch wear leading to damage and worn clutch packs. Analysis: - Resetting the GM Transmission adaptive learning to factory removes these problems, the trans will relearn bad behavior within 2-3 weeks of daily driving. Reset was performed using an Autel Hot function “Quick Learn” procedure for the transmission.

Filed Sep 1, 2026 · Transmission · NV

Factory powertrain programming actively locks out 9th gear (overdrive) during freeway driving at speeds exceeding 60–65 mph. The vehicle refuses to upshift from 8th to 9th gear, forcing sustained high-RPM operation during standard highway cruising.

Filed Jul 13, 2026 · Transmission · WA

Leaking transmission fluid at 7,000 miles. Technicians noticed during routine oil change at dealership.

Filed Jun 23, 2026 · Transmission · GA

The vehicle has experienced a recurring transmission-related defect that has required multiple repair attempts by an authorized GMC dealership. The transmission system has also exhibited fluid leakage. Despite prior repairs, the problem has continued to reoccur. Transmission and associated transmission fluid sealing components. The vehicle is currently available for inspection upon request. A transmission is a critical safety component that transfers engine power to the wheels. A transmission defect or fluid leak can result in loss of propulsion, hesitation, inability to accelerate as expected, unexpected changes in vehicle operation, or transmission failure while driving. These conditions could increase the risk of a crash, particularly when merging into traffic, crossing intersections, or traveling at highway speeds. Transmission fluid leaking onto roadways or vehicle components may also create additional safety concerns. The vehicle has been presented to an authorized GMC dealership for diagnosis and repair on multiple occasions. The dealership has acknowledged and attempted repairs related to the transmission. The vehicle has been inspected and repaired by authorized GMC service personnel. No police involvement. No independent inspection has been performed at this time. Manufacturer-authorized dealerships have documented the repairs. Symptoms included transmission-related concerns and transmission fluid leakage. The defect first appeared while the vehicle was under warranty and has continued despite repair attempts. The recurring nature of the transmission defect and fluid leak has reduced confidence in the vehicle’s ability to operate safely and reliably. The vehicle remains under warranty and has undergone multiple repair attempts without a permanent resolution.

Filed Jun 18, 2026 · Engine, Transmission · NV

Accelerator lag from any speed or stop. The care will take several seconds to hunt for the correct gear before shifting to accelerate. Or it will delay acceleration for several seconds while your pressing the accelerator. No SES indicator active. Mechanics can’t find issues. Other owners on forum a report the same sluggish behavior. These 1.5 turbo cars seem to need a software fix that they are not receiving. It’s like the drive by wire doesn’t register. Affects any gm vehicle with the 1.5 turbo and 9 spd auto.

Filed Apr 20, 2026 · Transmission · GA

While driving the vehicle, the engine light came on, plus message board said service transmission and the engine went into limp mode. We let the car sit for awhile and checked the car. A scan said it was the pressure solenoid A in the transmission. The car sat for a day and the light was off. Drove the car and then it acted up again and now reverse doesn't work.

Filed Mar 23, 2026 · Transmission · 3,787 miles · WV

The contact owns a 2024 GMC Terrain. The contact became aware of a fluid leak underneath the vehicle. There was no warning light illuminated. The vehicle was driven to a local dealer, where it was diagnosed with a leaking torque converter seal, allowing transmission fluid to leak onto the ground. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was 3,787.

Filed Mar 11, 2026 · Engine, Fuel system · IN

I was driving the car on 12-22-25 I lost power my car died on i94. Battery died the dearlship couldnt get the code. Got the car back on 12-26-25. Engine light came on carrie gmc replaced battery . Car back on 12-29-25.. Engine light back on 12-31-25 car back on 1-8-26 replacled catalytic conveerted and oxy sensor. 2-20-26 driving on 1-94 lost engine power car back on 2-25 feul pump and feul line. Drove 300 miles engine light back on. Back to currie gmc on 2-26-26 untill 3-2-26 replacred heated oxygen sensor . 3-6-26 replaced catelytic converter and oxyger sensor for the second time.

Filed Mar 4, 2026 · Transmission · OK

I bought my car in July of 2025 and since then my car keeps derating and reducing engine power while driving down the road at 70 miles an hour. It cuts out and decreases power. I took my car to the shop twice to have them tell it needed an update. I drove away and then the car does it again. Since December my car has down this decreased power, derated notice more than 30 times!! It is a safety risk for me and my family because you never know when it will happen on the interstate and when you will lose power. I have almost been rearended 3 times due to this issue and no one can seem to fix the issue.