Stuck in First Gear
Earlier this year, GM admitted that some 2025-2026 Chevrolet Equinox and GMC Terrain SUVs had a tendency to get stuck in first gear. Back then, dealers got a heads-up about the problem, but there was no real fix – just some tips on spotting the issue and a lot of crossed fingers while everyone waited for a proper solution.
Now, a new GM service bulletin says the company has finally hunted down the culprit and cooked up a fix. This time, the spotlight shifts to a new cast: the 2024-2026 Chevrolet Traverse, 2024-2026 GMC Acadia, and 2025-2026 Buick Enclave, all running the 8-speed 8T65 automatic. The good news? Unlike the earlier vague instructions, this bulletin provides technicians with a clear roadmap to a lasting repair.
GMC
A Sensor That Can Confuse the Transmission
The heart of the problem is a finicky transmission output speed sensor. This little gadget keeps tabs on how fast the transmission’s output shaft is spinning, feeding that info to the control module so it knows when to shift. But if the sensor starts sending out bad data – even for a split second – the transmission gets confused about what’s actually happening under the hood.
GM says the sensor can occasionally send out a bogus signal. When that happens, the transmission’s brain panics and decides to just hang out in first gear instead of shifting as it should. For drivers, that means the engine keeps screaming at high revs, stubbornly refusing to move up to second.
What makes this gremlin extra sneaky is that it can vanish without a trace. The bulletin says if you stop the car and shift into Park, the transmission’s brain resets itself. Fire it back up, and everything seems fine – until it isn’t. That makes the problem feel totally random and tough to catch when you finally bring it in for service.
GMC
GM’s Repair Procedure Is More Involved Than It Sounds
Even though the sensor is the main suspect, GM doesn’t want dealers to just start swapping parts, according to GM Authority. The bulletin tells techs to scan for trouble codes first and clear up anything they find. Only if the codes come up empty and the car is still stuck in first does the real repair begin.
If it turns out the sensor needs replacing, buckle up: it’s buried deep inside the 8T65 transmission. Getting to it means tearing apart a good chunk of the transmission’s guts, so this is definitely a job for the dealership pros.
GM is quick to point out this isn’t a recall – just a heads-up for dealers on how to handle the issue. So if your Traverse, Acadia, or Enclave is revving like it’s stuck in a drag race and won’t shift up, mention Bulletin #26-NA-192 when you book your service. It might just save you some time at the shop.
Amos Kwon
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