This Synapse Transmission Control Module (TCM) is a fully remanufactured, stock‑calibration Allison controller for 2006–2008 GM 6.6L LBZ and LMM Duramax trucks, built as a direct replacement for failed A50/T14 modules while retaining factory shift strategies and emissions compliance. It is a plug‑and‑play exchange unit that arrives VIN‑programmed for your truck, making it ideal for owners who want OEM‑correct operation and reliability.
The Synapse remanufactured Allison T14A / A40 Transmission Control Module (TCM) exchange unit is a pre-programmed, plug-and-play solution for 2006–2008 GMC Sierra 2500HD and 3500HD trucks equipped with the 6.6L Duramax and Allison 6-speed automatic transmission. Each module is fully remanufactured, thoroughly tested, and configured for your application to permanently address common TCM failures that cause limp mode, harsh shifting, and communication errors. An upfront core charge is required and refunded when a rebuildable original T14A/A40 core is returned within the program terms.
This unit is intended for trucks originally equipped with the T14A or A40 style Allison TCM; always confirm your original module’s family and application before ordering.
Common symptoms of a failing T14A/A40 Allison TCM include:
Before condemning the TCM, verify power, ground, and harness integrity; once external causes are ruled out, a remanufactured module is often the most reliable fix.
Synapse remanufactured TCMs follow a warranty model similar to leading Allison electronic reman programs, typically offering up to a 2-year warranty to the original purchaser against defects in materials and workmanship. If a covered module fails within the warranty period due to internal component or workmanship issues, it may be repaired or replaced according to the warranty terms. Failures caused by wiring problems, improper installation, or other vehicle issues are generally excluded from coverage.
| Feature | Synapse reman T14A/A40 TCM exchange | Typical used/salvage TCM |
|---|---|---|
| Module type | Remanufactured, bench-tested, pre-programmed for application | Used, pulled from unknown donor vehicle |
| Programming | Configured for your truck; generally plug-and-play with no dealer visit needed | Often requires separate programming or reflash |
| Root-cause repairs | Known weak points addressed during remanufacturing | No preventative internal repairs; unknown internal condition |
| Warranty | Structured reman electronics warranty (up to ~2 years typical) | Limited or short seller warranty, if any |
| Core program | Upfront core charge refunded when rebuildable core is returned | Usually no core return; single-use purchase |
| Risk of early failure | Reduced via testing and upgraded repairs | Higher due to age, unknown history, and original design weaknesses |
This remanufactured module is intended for 2006–2008 GMC Sierra 2500HD and 3500HD trucks with the 6.6L Duramax and Allison 6-speed transmission originally using a T14A or A40 TCM; confirm your original module’s label and application for best results.
No dealer programming is typically required, because the Synapse exchange TCM is shipped pre-programmed for your vehicle so it installs as a plug-and-play unit; after installation, you simply reconnect the harness and clear any stored codes if necessary.
Common indicators include codes such as U0101, U0100, P0700, or P2669, harsh or erratic shifting, limp mode, gear indicator problems, and periods where the vehicle loses communication with the TCM.
A refundable core charge is added to your order; once you have installed the Synapse module and the truck is operating correctly, send your rebuildable original T14A/A40 TCM back within the allowed time using the provided instructions. After inspection confirms the core meets the program requirements, the core charge is credited back to you.
Most core programs require a complete module free of catastrophic fire or water damage; heavily damaged TCMs often do not qualify for full credit, so such cases are usually evaluated individually and may receive reduced or no core value.
Replacing the TCM is very effective when the module itself has failed, but issues such as wiring problems, poor grounds, low fluid, or internal transmission damage can cause similar symptoms; a proper diagnosis should be performed before installing any new or reman module.
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