09 Express Van LMM 4l85e to Allison 1000

[JHP]

Could anyone help me with what I would need to do to swap the 4l85e for a Allison 1000.
2009 Express LMM.
I tried google searching but everyone is saying something different.
What I have gathered is I need to flash the ECM to a truck OS, repin the harness and get a T42A TCM correct?
Anyone done something similar, what all did you run into doing this swap, or any guidance on what all I will need electronically to make it work.
Thank you

 

[Jakezed22]

I know with guys wanting to swap and run the 4l85, they need to run van OS, re pin and get the 4l85 tcm. So just the opposite of what you've said. You should be on the right track.

 

[JHP]

Thanks Jake, I wonder if anyone can confirm the TCM needed

 

[JoshH]

They used the A40s and A50s back during the LMM years, but I think they have changed designations to T14A now.

 

[Chevy1925]

They used the A40s and A50s back during the LMM years, but I think they have changed designations to T14A now.

Correct