Duramax/4L85E wiring

MAXX IT OUT

<<<IT WORKS
Mar 1, 2013
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Des Moines, Iowa
How do the factory vans run the 4l85E? I have finally found a engine and trans for my c10 swap, but it doesn't have the ECU's or body harness. How different is the van harness from the truck harness? I have a truck harness and that I was planning on making a standalone, but I am not sure I want to do a manual valvebody or a separate standalone trans controller. I have a ls 4L80E wiring I could use, but I don't what GM used for a TCM in the Vans.
 

THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
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ZEPHYRHILLS, FL
GM used the T42 TCM for the 4l85e behind the duramax. The ECM is pinned slightly different so you can't run a truck tune in a van or vice versa, but the ECM's are the same so you can flash in a van cal to a truck ECM if needed. I haven't done it, but I know others have repinned van harnesses to run with a truck cal and allison, so I don't see why you couldn't do the same in reverse if needs be.
 

JoshH

Daggum farm truck
Staff member
Vendor/Sponsor
Feb 14, 2007
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Texas!!!
I repinned my van harness to run a truck cal with the T42 because I wanted to be able to run a DSP OS.