I have a 2004 Trailblazer EXT with the LM4. The engine and transmission are on their last leg and I was thinking about swapping in a L92 with either a 6L80E or 6L90E. Originally I was looking into swapping in a 4L80E, so I know I'll have to have a transfer case pattern conversion ring made and also have the input shaft on the transfer case re-splined. My main concern is the electronics. Most of my GM knowledge ends at 2002. I've researched some and am thinking I could basically leave the engine/transmission wiring alone between the engine, transmission and ECM. It looks to me like I could use an E67 ECM to run the engine, communicate with the transmission controller and then utilize the E67's Class II Data Bus signal to talk with everything left on the Trailblazer (BCM, Radio, Transfer case controller, ect.)

Has anybody done this, or something similar? Does this sound right, am I missing anything?

 

This is definitely in @1FastBrick 's wheelhouse, he's talked about stuff like this before

I would consider changing t cases to either a manual case or a normal pattern auto case that can communicate with your TCCM. Stacking adapters and resplining sounds like less engagement and less material available to handle stress to me

 

there using a trailblazer operating system from the last year I believe and then wiring up the 6l80e

I am not sure about the body control side though on a Trailblazer. But it has been done in the gmt800 trucks successfully.

 

I've looked into other transfer cases when I was thinking about the 4L80E, I didn't see many people with any experience swapping to another electric transfercase on this platform. I do have an electric shift transfercase out of an 03 2500 that had an 80E in front of it. Maybe I'll play around with that and see what I can turn up. I'm not planning on super high numbers with this build, basically just the L92, cam, tune, LTs (which I already have on the LM4). I would love a Whipple, Magnacharger or LSA setup, but the odds of that are basically nil.

 

I'll take that as a good sign if people are using the Trailblazer OS. I've looked at the wiring diagrams from the older Trailblazers like mine and the newer ones. The newer ones have 2 "High Speed GMLAN Serial Data" wires that go from just the PCM to the TCM, along with Class 2 Serial Data lines. The older system doesnt have the High Speed GMLAN, but the Class 2 Serial Data diagram is basically identical to the newer platform's Class 2 Serial Data diagram.
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I suppose one could use the Trailblazer operating system and segment swap in the L92 and 6L80E/6L90E.