I have the opportunity to buy a 2011 6.2, 6l80 and AWD transfer case from a Denali and it comes with the entire engine harness and ECM, the TCM is internal to the 6l80. I want to put them in my 07 avalanche 4wd which currently has an 5.3 4l60 but I want to keep a 4hi/4lo transfer case. I know I’ll need a 6l80 autotrac transfer case for the spline count, but the AWD case is just a dumb case with no electronics so I’m struggling with how to integrate this.

Do I use the 2007 ECM, and have it flashed for the 6.2 and 6l80 with a mail order tune, or do I use the 2011 ECM and have it flashed somehow to know it’s got a real transfer case now? Do I need to use the 2007 harness since it has the transfer case wiring or is that separate from the engine harness? What about all the VINs in the ECM, TCM, guage cluster, BCM, all that stuff? HP tuners? Do I need a shift stalk with the manual mode buttons and a new 09+ cluster to see the gears?

Has anyone ever done this before? And no I don’t just want to sell my truck and buy a 5.3 6l80 avalanche and just swap the 6.2 and do a lift again. The trans seems to be the biggest issue, and I don’t (yet) want to do a 10 speed conversion as that’s another $5000 with the conversion harness.

any hints on what I need? Where to start? Don’t do it?

 

your 07 is a nice looking rig, you've kept it well.

MY recommendation is to keep the 5.3 liter, give it a mild truck camshaft, around 8 to 10 PSI manifold PRESSURE and a 4L80 transmission.

 

I think the clearest path forward for you is to compare the pinouts of the 2007 ECU to the 2011 to see how close they are. Quick google search shows that you should have the E38 ECU which should make your life much easier. My suggestion would be to use your stock ECU so that it will communicate with everything stock in the truck you are keeping and have if flashed to control the 6l80e (may need a different TCM) and of course the engine. You'll just need a new transfer case that will work with the 6L80e and give you the high low. You'll also need to figure out if the wiring is compatible. I'm sure that you can get it all to work together because I'm pretty sure that same combination was available in other model trucks. My dad had a 09 Silverado 1500 with an L92, 6 speed auto and high low transmission.

 

The truck is rust free, and has the lift which keeps the bumper and everything out of the water when I launch on our not steep neighborhood ramp in salt water. I have to go in up to the rim to get the boat off, and waves would touch a normal truck bumper. Downside is the guy before me tried to run 35s with a smaller lift and he beat the crap out of the inner fenders to clear and rough cut the bumper, then eventually he put the right lift on it. The 5.3 4l60 does fine as a DD and towing my 5500lb boat, but I’m looking at a 9-10000 lb boat and need more gears and power, and need to keep true 4x4 for low tide slippery ramps. From what I’m reading I think the swap will work, but the BCM and making sure the transfer case work are my variables I havnt figured out.

 

I have a "Hoe" on 35 inch WildPeaks.
4.56 axle gears made it a LOT more fun.
Magnuson blowing 11 PSI helps a bit as well.