"Allison" 10 speed hard upshift gears 7-8

MORSNO · July 27

17 hours ago, UWSkier said:

Finally got into a dealership to have the shift relearn done and it's back to shifting smoothly. It took 11k miles before it started acting up before. Hope it's good for at least a few thousand miles of towing before it hits again. Really sucks not having 8th gear on a cross country tow.

Keep us posted on your results please.

Another JR · July 27

10 minutes ago, MORSNO said:

Keep us posted on your results please.

Is “relearn” really just a “control-alt-delete” by disconnecting the power long enough for memory to clear, or was it a load of a new software version? If it was just a reset, we should be able to just do it ourselves. I know on earlier vehicles I could do this to correct certain bad shifting characteristics that had developed over time.

newdude · July 27

22 minutes ago, Another JR said:

Is “relearn” really just a “control-alt-delete” by disconnecting the power long enough for memory to clear, or was it a load of a new software version? If it was just a reset, we should be able to just do it ourselves. I know on earlier vehicles I could do this to correct certain bad shifting characteristics that had developed over time.

Requires GM's diagnostics software GDS2.

It "might" be possible to access with a higher end scan tool but I've seen issues even with up to date current Snap On scanners not being able to perform functions on GM vehicles with GM Global B architecture, like the 2024+up HDs for example.

The Service Fast Learn or the Transmission Adaptive Pressure Reset for this 7-8 shift is only a temporary solution as GM is still investigating what exactly is going on.

Edited July 27 by newdude

UWSkier · July 28

10 hours ago, newdude said:

Requires GM's diagnostics software GDS2.

It "might" be possible to access with a higher end scan tool but I've seen issues even with up to date current Snap On scanners not being able to perform functions on GM vehicles with GM Global B architecture, like the 2024+up HDs for example.

The Service Fast Learn or the Transmission Adaptive Pressure Reset for this 7-8 shift is only a temporary solution as GM is still investigating what exactly is going on.

Yeah, I know it's only a temporary fix, but since it was fine for a year, I'm hoping it's fine for another year after having this done. At least I hope it's fine for my camper tow from WI back to AZ next week, as it was lame going cross country without being to use 8th gear. I also wanted it done so there's a service record of my truck having the issue so I can hopefully get faster service once the fix is released. Crazy they've been working on this for months with no update though. Seems pretty obvious there's a software issue. Not sure if they have an ability to flash a firmware update but it'd seem that's the fix since it's clearly nothing mechanically wrong.

UWSkier · August 9

1000 miles into the tow after the relearn and 8th gear shift is working flawlessly. Great to have it back as it's where the truck is happiest towing the camper.

MORSNO · August 10

22 hours ago, UWSkier said:

1000 miles into the tow after the relearn and 8th gear shift is working flawlessly. Great to have it back as it's where the truck is happiest towing the camper.

Good to hear!