This is my first 4x4 truck, (1992 22re 5spd), its a daily driver, bought it to travel to fishing holes and ski hills, is there such a thing as "highway gears" to increase fuel economy? Can I change the rear end gearing for better mileage. I assume the front and rear DIFFs have to be geared the same? I changed the rear DIFF in my old Buick GS (rear wheel only) from sport rear end to Highway rear end and it increased the mileage. May not apply to 4x4...looking for suggestions.