[RetiredEng]

The L4, L5, and L6 out of the GMT360 Trailblazer and all variants are the same engines as far as possible. Obviously different cranks, cams and stuff like that, but pisions, rods, and others are the same.

 

[RetiredEng]

The L4, L5, and L6 out of the GMT360 Trailblazer and all variants are the same engines as far as possible. Obviously different cranks, cams and stuff like that, but pisions, rods, and others are the same.

Well they were supposed to be as common as possible.

 

[RetiredEng]

I guess I hit my first roadblock. I was able to put the pilot bushing from the 3.7 into the 2.9 and was ready to put the 2.9 in. When I noticed the 2.9 was out of a stick shift and the harness that came with it doesn't appear to have the wiring for an automatic. I'm sure I just have to get the right harness but it stopped my progress.

You'll need the Transmission Control Module as well as the harness and a bracket to hold the TCM on the firewall. And probably some reprogramming of the ECM to tell it to look for messages from the TCM as well as transmit some messages to the TCM. And to tell the ECM that you have an M30 (I assume) and that the truck has an automatic now. It's doable, as a lot of people here have done things of this sort. But it's not that straight forward, there are a lot of subtle things to do if you want to get it to be like the factory built it that way. Does it have to be that way? IDK! No doubt more knowledgeable people who have done this before will respond eventually.

 

[RetiredEng]

Jacobg98 may have better experience than me about this, this is a mechanical engineer domain, but having worked in powertrain, for the 355, 345 H3, and 360 Trailblazer and all of their variations, there was a deliberate effort to keep the L's 4, 5, and 6 as common as possible. As much as was possible, they literally took 1 cylinder off the L6 to make the L5, and 1 more off to make the L4. Obviously crank, cam and stuff like that isn't compatible, but stuff like the sensors, pistons, rings, sleeves if any, I would think are. I am not an expert on the specifics, but if Rock Auto says they are the same, I wouldn't be surprised and would believe it. I was on a few development rides with the Chief Engineer for all 3 of those engines and he talked about that when we were riding in the same truck.