This week we changed the gearing on the truck from 3.73 to 3.42, installed a Yukon free spin hub kit among other things.
https://www.yukongear.com/spinfree.aspx
The steering box and linkage was replaced, and ball joints as well.
Initial results were very gratifying. In a short test of a few hundred miles, I got about 15% better MPG than the best tank in the previous 15 months of ownership. It was not ideal driving speeds either, some of it over 70 MPH.
I could not be more pumped. The truck is approaching the economy of the 2wd 12V with no aero mods, and retains all the 4x4 capabilities.
If you were to ask how much was due to the spin free hubs and how much was gearing, I'd just grin and tell you I don't care
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2007 Dodge Ram 3500 SRW 4x4 with 6MT
2003 TDI Beetle
2002 TDI Beetle
currently parked - 1996 Dodge 2500 Cummins Turbodiesel
Custom cab, auto, 3.55 gears