Oh and I found out why the factory wiring diagram did not show the 2-w / 4x4 selector switch wasn't shown.
After talking to a very knowledgeable guy about it he said it never had a "factory" selector switch, it was a service bulletin if the customer wanted to manually select 2wd or 4wd vs auto 4x4.
He clued me into the wiring and all is good!

TURBS
08 duramax tuned n modded
2011 32bhok Sabre
2015 camping "9 nights"