I would bet there's probably some tweaks in that whole mess of dod stuff that could probably help the cause but it's not somethin ive really ever messed around with or tried comparing between different vehicles to even know where to begin without some trial and error.
The 3.08s getting better fuel mileage makes alot of sense though if it sits in a little sweeter spot in the rpm band for cruising. I'm over here gettin maybe 15 or 16 unloaded and 10 to 11 with the trailer on regardless of it's got 87 or e85 in it. Should probably put an actual flex sensor in it once I sort out the rich fuel trims.
And then there's brakes. 4 wheel disc's are great but it's time for pads and one of the calipers is a little squeaky so I'm sure the slides are in fantastic shape lol
I had the truck dyno tuned back in 2010, the only mod being 89 octane instead of 87 to get the knock retard down. It really cleaned up the mapping and fuel economy/performance noticeably improved. The tuning of the DoD was still a mystery back then, and the tuner tried messing with it to get it to work better. Eventually I was able to hold 72mph and stay in 4cyl mode which netted me about 20mpg. However the transition from 8-4 and 4-8 was really pronounced and uncomfortable. The tuner "claimed" he rolled back the changes and left the rest of the tuning in place, but I'm 99% sure he just flashed everything back to stock. He then ghosted me. For a "professional tuner and engine builder" that really pissed me off.
GM should have figured a way for the driver to set the aggressiveness of the DoD while driving. There is no reason that while cruising at 68mph that 1-2% throttle input with minimal engine load should put it back into v8 mode. Even with the mileage and age of the truck I'd like to get the DoD working better, if at all possible. I know the oil consumption increases the more the DoD engages, but it has never been an oil burner, so not worried about it.
As for the gearing and "sweet spot", at 70mph I'm right at 2000rpm (stock tire size of 265/65R18). My dad is about 1800rpm at the same speed (also stock sized tires).
I really do like the truck and intend on keeping it as long as possible.
Oh, and I don't have the towing package, so front disc/rear drums. I just had the rears replaced last week. Was on the factory shoes and drums, with the drums having been turned once, about 130k miles. I was pretty sure the shoes and drums would be almost nonexistent after nearly 200k miles. When the mechanic pulled the drums a shit ton of dust/rust fell out, and you could see some scoring on the insides, but tons of metal left. The shoes, the shoes looked to still be about 90% material left. I was flabbergasted.
When was the last time someone used flabbergasted?
Right rear rear-facing shoe (they all had equal amounts of material on them):
