2015 GMC Sierra 1500 transmission problems

Filed Oct 21, 2026 · Transmission · TN

The 6-speed automatic transmission (6L80) developed a severe shudder during normal driving. A service center diagnosed the problem as torque converter clutch failure; the torque converter sheds metal debris through the transmission, so the transmission now requires a full rebuild quoted at approximately $6,000. The failure occurred at approximately 92,000 miles in October 2026 (incident date is approximate). This is a widely documented failure pattern on GM 6L80 transmissions. Loss of reliable power delivery from the transmission is a safety concern. No crash, no injuries, and no fire occurred. The vehicle is available for inspection upon request.

Filed Sep 22, 2026 · Transmission · FL

The transmission Started Shuddering, it would slip occasionally and slipped badly when i was driving in rush hour traffic in the middle of a left turn. had no power for several seconds then it finally reengaged. The shuddering got worse and worse to the point i took it to a transmission shop to look at it and they said i needed a replacement transmission unit. I did get a replacement unit, the whole process was extremely unpleasant. The previous unit was sent as a core to be remanufactured. The company that i used to get a remanufactured unit is Fraser Transmissions. No warning lamps appeared prior to the transmission acting up.

Filed Sep 10, 2026 · Electrical, Steering · IL

Power steering seems to be lost for a second or two at low speeds turning. Happens multiple times a day.

Filed Aug 6, 2026 · Transmission · NE

My 2015 GMC Sierra 1500 SLE has the 6L80 transmission. While traveling on the interstate with my fiancé, the transmission failed. It was towed to a garage and they informed me that it needed to be replaced.

Filed May 26, 2026 · Electrical, Transmission · RI

For no apparent reason the truck goes into “low power mode” and gives off code p2138 often happens around 30-35 mph. Have had it happen to me also around 45 mph also. I have replaced sensors and parts to which a month or so goes by and it happens again.

Filed Feb 18, 2026 · Transmission · WA

During day to day driving when the truck is accelerating from a stopped position there's a massive clunk or hard shift from either 1st to 2nd gear. have also heard similar complaints from other 2015 sierra 1500 owners saying the transmission is having a hard shift on acceleration from a stop. Have seen possible issues with the TCCM

Filed Feb 17, 2026 · Transmission · OH

Tranmission is shuttering and not wanting to shift right

Filed Feb 10, 2026 · Transmission · 225,740 miles · LA

The contact owns a 2015 GMC Sierra 1500. The contact stated that while at a complete stop and attempting to shift into reverse(R), Drive(D) or park(P), the gear shifter was stuck, and the contact had to go underneath the vehicle to move the shifter cable into the intended gear. The vehicle was taken to an independent mechanic, where the upper and lower shifter cables were replaced. The contact stated that upon returning to the residence and attempting to park the vehicle, the gear shifter failed to remain in the intended gear and was moving unintendedly. The vehicle was not repaired. The dealer and the manufacturer were not contacted. The failure mileage was approximately 225,740.

Filed Oct 18, 2025 · Electrical, Transmission · MA

The temperature sensor in the transmission is faulty leading to hard/delayed shifting, shuttering, and vibration

Filed Oct 15, 2025 · Transmission · WV

Transmission failed at 110k miles roughly. Safety was put at risk due to this happening on a highway. Yes, transmissiom was replaced by a local repair shop, the means of failure was identical to thousands of vehicles in this model year failing prematurely. No it wasnt inspected by the dealer. No there was no warning light, we were going up a hill and it failed.