Hey my name is George and I'm from Oklahoma. I have a 06 Chevy Silverado 1500 regular cab short bed 4×4 Z-71 w/5.3l and 4l60 I have swapped out the transmission dues to no drive gears, now I have no reverse. The transmission looked great bought it online but the main plug is blue and brown on the transmission but on my truck it's green. Could this be what is stopping me from having reverse? The OBD2 scanner says P0785 and P1810.

 

I am not up on which year transmission work with each other, but I am thinking the 2 transmissions are incompatible without swapping some parts around. Hopefully someone who knows for sure will step in. I do know though that is not the reason for no reverse. This trans does not need any electrical for reverse to work. You can unplug the harness from the trans and you should still have reverse and 3rd gear.

 

Well. You have 2 issues. 1 the new trans is bad as regardless it should have reverse . But in addition the BLUE BROWN connector is 09 up and the electronics are incompatable with your 06 truck. Normally I would tell you how to swap VB / electronics and shifter rod to allow it to work. But with no reverse its a no go situation.
So try again on the Trans , Any model year from 2000 to 2008 with a 300mm shaft and 4x4
You can use the green center or brown center plug style. Note some afternaket harnesses I have gotten of late do not have those color designations , But looking at used trans its unlikely the internal harness has been changed.
I have a post someplace on my FB thats lets you identfy by the tag on them ill try and find and post later.

 

Assuming your shift linkage is working and you have Park (with Reverse next to it), and you have correct level fluid in the trans, then as Mr Bond stated, you should have Reverse, even with the trans harness disconnected or, as Frank thinks, you have an incompatible year trans.
Check you linkage and fluid level again if unsure. Do you still have the online ad for the trans. Did it mention a year? Did it perhaps list it as a 4L70E or 4L75E?

 

This is why I used to Build my Internal Harnesses with a "Keyed" TPA for the Main Electrical Connector...
There is only one Matching Connector that will Mate with the "Keyed" Internal Harness.


But then I had some Customers get upset that they needed a "Special" Mating Electrical Connector...
So I stopped doing so.

But it makes sense to me,to not have these Different Internal Harnesses all Mate with the same Key-way when Delphi already made a few different Keyed TPAs.

 

Delphi produced many different TPAs for what we use as the 4L60E/ 4L80E Transmission Connectors.

They were produced in different Colors, Pin-Counts, and Key-Ways.
There are maybe 40 different Variants of TPAs.

Here are just a few Examples of the different Key-Ways...
The "Standard" Keying is shown in the Center Position:





The Different TPAs of course need Matching Mating TPAs.
Below shows a Keyed Set of TPAs/ Connectors that would NOT Mate with any of the "Standard" 4L60E/ 4L80E Connectors: