Has anyone changed to taller gears for sake of increased mileage. I drive 50-60,000 mi/yr. Truck is used 95% for transportation. When I have towed with it it handles towed loads without using tow/haul mode. Truck is 2003 wAllison 2wd no mods yet.
I can get 18.25 mpg if I keep engine rpm's around 1800rpm. I have a K&N FIPK w/AFE filter, lift pump w/aux filter, modified left ex manifold to flow freer, 17" Hummer wheels w/Michelin which are stock dia. If I pull a trailer empty or loaded 13.75mpg.
I looked into it a few years ago but at the time you could not buy any taller gears for the Duramax axle. Not sure if that has changed today but that pretty much stopped the idea back then. I figure a 3.55 or 3.42 would be nice.
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