GM has identified the cause of a transmission problem affecting certain SUVs and issued a service bulletin outlining a repair. The issue can leave some 2024-2026 Chevrolet Traverse, 2024-2026 GMC Acadia, and 2025-2026 Buick Enclave models stuck in first gear with the 8-speed 8T65 automatic transmission.
GM Identifies the Transmission Problem
Earlier this year, GM acknowledged that some 2025-2026 Chevrolet Equinox and GMC Terrain SUVs could become stuck in first gear. At the time, dealers were informed about the issue and given guidance on how to identify it, but a permanent repair was not yet available.
A new GM service bulletin now identifies the suspected cause and provides technicians with a specific repair procedure. The bulletin applies to the 2024-2026 Chevrolet Traverse, 2024-2026 GMC Acadia, and 2025-2026 Buick Enclave equipped with the 8-speed 8T65 automatic transmission.
A Faulty Sensor Can Keep the Transmission in First
The problem centers on the transmission output speed sensor, which monitors the speed of the transmission’s output shaft and sends that information to the control module to help determine when the transmission should shift.
According to GM, the sensor can occasionally produce an incorrect signal, even if the problem lasts only a moment. When that happens, the transmission can respond by remaining in first gear instead of shifting into second.
For drivers, the result can be an engine running at high revs while the transmission refuses to shift normally.
The problem can also be difficult to reproduce. The bulletin states that stopping the vehicle and shifting into Park resets the transmission control system. After restarting the vehicle, the transmission may operate normally again until the problem returns.
Repair Requires Work Inside the 8T65 Transmission
GM’s repair instructions require technicians to begin by scanning the vehicle for trouble codes and addressing any codes that are found. If no codes are present and the vehicle remains stuck in first gear, technicians can proceed with the repair.
If the output speed sensor requires replacement, the repair is more involved because the sensor is located deep inside the 8T65 transmission. Accessing it requires disassembling a significant portion of the transmission.
GM’s bulletin therefore provides dealers with a defined procedure for addressing the issue rather than simply replacing parts without first checking for trouble codes.
GM Says the Issue Is Not a Recall
GM emphasizes that the service bulletin is not a recall. Instead, it provides dealers with instructions for handling the transmission problem on affected vehicles.
Owners of a Traverse, Acadia, or Enclave that remains stuck in first gear and continues revving at high engine speeds can reference Bulletin #26-NA-192 when scheduling service.
The new bulletin gives technicians a specific path to diagnose and repair the transmission issue affecting the listed GM SUVs.
