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ATS Diesel TCM Upgrade A50 to T87 For 2011-2015 Duramax LML

ATS Diesel TCM Upgrade A50 to T87 For 2011-2015 Duramax LML

The A40 and A50 TCM that is used to control the Allison 6-speed automatic transmission is the weak link of the 2011-early 2015 Duramax 2500/3500HD. This is due to delicate thin wires inside the TCM that contact one another overtime and short-out the entire module. In 2022, Allison sent out a letter (SIL 15-1K2K-22) announcing the discontinuation of support for the A50 and A40 TCM Controllers which is not good news for anyone with a 11-15 Duramax.


ATS is excited to release the new GM Allison T87A upgraded TCM module. The upgraded TCM comes in an assembly including the ATS Translator® module that also has our Co-Pilot transmission functions built in.



Works with stock or modified trucks.

Controls and increases line pressure.

Direct replacement, no permanent modifications required - plug and play OEM quality harness and module.

Found on the current 2023 Duramax, the T87a TCM has a much faster processor than the A50 and that equates to better shift quality, faster shifting and overall improved drivability.

Direct Replacement for AC Delco: TCM 24256861 25978353 15117030



New T87a TCM that is unlocked and has a custom ATS calibration pre-installed that optimizes the performance of the Allison transmission.

New Translator® module that has the Co-Pilot transmission pressure function enhancements built in. The Co-Pilot functionality allows the factory Allison transmission to handle higher power levels and much better durability.

Mounting Bracket

Wiring Harness

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