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Old 05-08-2014, 09:42 PM   #1
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Question for Tom Johnson

Tom,

I sure have appreciated all the knowledge you have shared with us here on this forum. When it comes to Allison transmissions, you are DA MAN!

Here's my situation...

2006 Freightliner XC-R chassis.
Cummins 400 hp ISL
Allison 3000 MH transmission

Every once in a while I'll get a flare on the 3-4 shift, at light to medium throttle. WOT shifts are firm and OK.

Is this something to worry about?


Rich & Linda
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Old 05-09-2014, 01:55 AM   #2
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Take it to an Allison dealer and get then to "Reset Fast Adaptive". Only takes a minute with their Allison DOC software. It doesn't change any settings, it just puts the ECU into a relearn mode where it is "allowed to make relatively large changes in the adaptive values after each shift".
Then take it for a good drive with lots of gear changes, especially the 3-4 shift you are having problems with.

Make sure they don't reset all shift parameters.
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Old 05-10-2014, 06:46 AM   #3
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Along this same line of questions.... I unhooked the Allison power from the chassis battery for a day. I heard that will reset the tranny and it relearns shifting patterns? What is it relearning?


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Old 05-10-2014, 08:30 PM   #4
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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.
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