2006 GMC Sierra 1500 - Wiring question

replaced the transmission in a 2006 gmc sierra 1500 4 wheel drive with a tranny from a 1999 chevy trailblazer, have no gears at all , is there a difference in wiring for signal to the tranny

Are you 100% sure this transmission is even compatible with the vehicle?

A Trailblazer and a Sierra are different vehicles. I think you mean “Blazer”, instead of “Trailblazer”, as the Trailblazer didn’t come out until the early 2000s. The “Blazer” may have used the same V6 as the 2006 Sierra…but I can’t say for sure.

I think the trailblazer will use the same 4l60e trans as the half ton trucks. A 1999 model will be drive by cable, a 2006 will be a drive by wire system. I don’t know what issues you’d run into in swapping a trans between those years / different systems.

Can the ECM of a 2006 vehicle “communicate” properly with the TCM of a 1999 vehicle, even if it was made by the same mfr? Somehow, I doubt if it is possible for the 2006 ECM to work with a 1999 TCM.

Yeah, I dunno. I was thinking some vehicles have a separate ECM and TCM, some are combined in one unit (I think). Never had the occasion to dive into it, so no idea on the vehicles in question. I’m assuming if you just swapped “hard parts” from the donor vehicle into the truck, and kept all of the truck’s harness, etc in place, the swap might work. I’d be surprised if the junction block where the harness plugs into the trans is the same on a 99 vs an 06, though. Wish I knew more about it and could be of some help, but I do not.

Your local auto-recycler will probably know the answer. Even a place like Pick-N-Pull has the database of compatible used parts for your 2006 GMC 1500. I have no experience with these make/model/years, but I’d pretty much presume there’s going to be considerable compatibility problems installing a 1999 xmission into a 2006 truck. More likelly to be possible with a manual transmission; I’m assuming by the trouble you are having it’s an automatic.

Part fitment can also be done by going to an a auto parts website and comparing part numbers. I took a quick look at your situation and the numbers are far different along with the converters.

There are also notations on both years about needing your VIN and there are variations in the same year model. So that brings up the question.
Where did you get the transmission?

As for the wiring itself, wiring can not only change by the year but also during the middle of a production run.