MYTH. Disconnecting the battery supply will reset an Allison ECU.
I have never seen in any Allison publication that disconnecting the battery supply will do anything to the ECU. Would love to see an official document to prove this commonly held myth.
Allison on highway ECU's from the World Transmission onwards have Adaptive Shift Logic programmed into them. These are the 1K, 2K, 3K, 4K, B400, B500, and T series transmissions with WTECI/II/III, GEN4, and now GEN5 controls.
These transmissions have a series of electrical solenoid valves that apply and release clutch packs for each gear. The ECU will power up one or more solenoids, which in turn will apply the required clutch packs for a particular gear. The ECU varies the rate that it powers on, and powers off, these solenoids to engage the clutch packs smoothly.
The new ECU comes with a base calibration (unadapted) and is set to Fast Adaptive. From the very first start it monitors every gear change and learns how the transmission changes gear. No two transmissions will behave exactly the same. While in this fast adaptive state it can make relatively large changes to how it powers up these solenoids, but eventually it gets to a converged state where it only has to make minute changes, if any.
Now once the ECU has got everything just right and all shifts are smooth and precise, why would the makers of the best on highway transmission in the world let you stuff it all up by disconnecting the batteries? It just doesn't make sense!
So show me where Allison says that disconnecting the batteries will reset the ECU.