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ATS A50 to T87 TCM Upgrade, Allison LCT1000, 2009-2010 GM 6.6L Duramax

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SKU: 601-146

ATS TCM Upgrade, A50 to T87
Fitment: 2009-2010 GM 6.6L Duramax

The A50 TCM that is used to control the Allison 6-speed automatic transmission is the weak link of the Allison transmission. 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. This effectively left over 10,000 Duramax owners out of their trucks. Some of the warning signs of a failing TCM are messages including “Service Brake System”, “Stabilitrak Service Required”, “Range Shift Inhibited”, “Service Brake System”. So we got to work developing a solution utilizing our Translator® technology found in the ATS Allison Conversion to help get these trucks back on the road, shifting and holding power even better than before, ASAP!

The ATS T87 Conversion now provides a much more aggressive factory exhaust brake over the factory A50/T14 TCM. We were able to increase the exhaust braking ability in two areas. First off, we enabled all of the additional tables that the T87 offers that are designed to operate the standard exhaust brake function and the Tow Haul exhaust brake function, these two tables are specifically designed to manage the exhaust brake and provide an aggressive down shift schedule. Secondly, we are able to command the ECM to use the full exhaust braking function of the ECM, the factory A50/T14 TCM limits this ECM from commanding the full exhaust brake. When the ATS T87-Translator upgrade is installed we enable the ECM to apply the full exhaust braking effort the engine has available. The combination of the T87, custom TCM calibration and Translator module maximizes the Transmission and Engine/Turbo exhaust brake to provide the most aggressive exhaust braking yet! This function not only provides a safer level of driving but it gives superior engine braking reduction with heavy loads.

The A50 TCM have been used in all GM Duramax/Allison Diesel Trucks produced from 2006 to 2017. ATS is excited to release the new GM Allison T87A upgraded TCM module. The upgraded TCM comes in an assembly including our Translator® module that also has our Co-Pilot transmission functions built in.

No core charge required, all components are brand new. GM has released a “Band-Aid” fix which repairs the problem but does not fix the root cause. This repair requires a trip to the dealership which can then take up to a week or more to make it through the service department, costs nearly as much as our upgrade, and leaves the same components vulnerable to reproducing the same problem with no warranty on the repair.


  • 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
  • Increases throttle response
  • Fuel economy and MPG improvement
  • Updated shift points to keep the engine within desired RPM range
  • Better torque converter lock-up response
  • Increases life expectancy of the Allison LCT1000 Transmission
  • Brand new, factory sealed TCM
  • Our complete wiring harnesses use state of the art technology and configuration
  • Can be used with any Engine Control Management programming
  • 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

Instructions Coming Soon

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