well that settles it, the 6L80 and whatever transfer case is bolted behind it is for sale.
120 something thousand miles
I had a böner for a 6L80E swap and researched the hell out of it. A friend swapped a 6L into his '07 Silverado, so I was able to reference him. It would "work", but he didn't know what gear he was in (truck had original cluster) and couldn't use tap up/tap down to manually select gears. I forget exactly what for, but he used a Raspberry Pi module with some custom programming to make something small, but necessary work. The controls go through the BCM, so you'd need to have a way to program that as well as the PCM. By comparison, the wiring is the easy part. Ultimately, I found that it'd be much easier (and WAY cooler) to swap in a manual trans, including sourcing manual trans truck parts from Brazilian models. (Models of trucks built for the Brazilian market. Not Brazilian hotties that sell obscure truck parts.)
If you wanna compare schematics, you probably could swap the powertrain harness and cluster over from the Sierra and have the 6L. Could have VVT as well. You'd still have a lot of labor and would still need to find a way to program the BCM. Speaking of VVT, you could trim that circuit from the Sierra and add it to your '08's harness. Have that turned on in the tune and enjoy a broader powerband.
Long story short the sierra was wrecked and I bought the Tahoe with 198k. Power train in sierra is solid and the Tahoe is starting a very faint tick. The oil sample I sent out to the lab came back with high levels of lead. I'm just getting ahead of the problem because I have the hardware sitting here. Im hoping it'll go to 300k before I need to swap but when it goes I'll have the engine from the sierra ready to drop in, weekend job. Back to work on Monday. At least that's my plan....
Oof. Sorry to hear of the lead. We have so many similarities here. These things are solid, indeed. I did the refresh and hot-rodding to my LMG right at 200K. Literally hit 200K at the dragstrip while getting stock baselines, went to dinner, then home and tore into it the next day at around 200,030 miles. I never cracked apart the bottom end- compression and cylinder walls were great. Cam bearings had the expected wear and I would liked to have changed them. But, at that point, it would've turned into a full rebuild. All I was originally aiming for was to replace all the seals/gaskets and delete AFM. I justified my mods as they could either be sold or used on another build. My hooning for the past 21K miles has been documented here. I've towed long distances (Tampa, FL to Baton Rouge, LA) and taken plenty of two- and 5-hour weekend trips. Just took a road trip to Tampa and surrounding areas back in November- 2,003 total miles including a few 135+ MPH jaunts.
About six weeks before that Tampa trip, a valve spring broke (defective batch). I buffed out the piston face, replaced the bent exhaust valve and slapped it back together with some copper spray on the reused Cometic gasket. All new valve springs, of course. Before I found out how minimal the damage was, I bought a spare engine to have at the ready, just in case mine was trashed. Ended up with a 140K-mile LC9 from a Sierra. It's an '08 or '09, so no VVT. I haven't opened it up yet. Current plans are to build it identically to my LMG so it'll be a plug-and-play long block to minimize downtime for when I pop my LMG. I'll then have the LMG to build up since it's an iron block and I want a turbo.
