So I'm planning a project for my trailblazer (5.3l w/4l60 & np226) and I think I have settled on the configuration as I've always wanted a six speed in this truck. I'm mainly planning this for street use but I will probably be moving to Colorado in a year so want to keep the 4wd.
I have a low mileage 2007 6.2L L92 motor from an Escalade sitting in the garage and I currently have Shift Rite Transmissions sourcing the 6l80(six speed trans) and np246 (transfer case). I would have liked to go with the 6l90 trans and MP3024 (NQH) TC from a Silverado 2500 but I wasn't sure about the TCCM controlling the newer TC or what would happen if I swapped in the 2500's TCCM. They have the same connectors but I don't know if the BCM would freak out and/or my dash switch would be compatible.
I know people have put the 6l80 in the TB before with the stock transfer case and I also know that EricSS has the np246 is his SS so I am fairly certain that I won't have clearance issues.
I know I will probably have to modify the trans crossmember and will definitely have to shorten/lengthen the driveshafts.
I haven't decided to stay with the 3.73 gears I have now or go down to 3.42 yet. The first gear in the 6l80 is 4.03 so if I stay with the stock gears it would be that same as if I put 4.88's in with the stock four speed trans! I think the plan is to get a junkyard front diff with 3.42's in and pick up a SS rear (14 bolt w/ lsd) and swap the gears. I would need to get some type of Limited Slip with this setup anyways.
I have two routes for the wiring. tbmsport.com sells a nice 4l60 to 6l80 adapter but it is pricey or I could have the harness modified by a very competent local guy.
Fortunately in Tampa we have a few options for excellent tuners so I think I don't really have to worry about the computer other than there isn't a specific VIN to reference that has this engine/trans/tc combo.
Any thoughts?