I have an 83' F150 5.8L 4X4 that gets around 11mpg.....I was wondering what gearing could be on this truck. I am planning on putting 33"-35" X 12.5" tires on and was wanting to know what gearing I could go 2 to save as much gas as possible? I am not worried about pulling power as I don't care to tear my truck up. Also it has an automatic transmision that seems to jerk when I put it in gear and it changed gears (even down shifting). What could the reason for this be?

 

What's the axle code on the door sticker? What size tires are on it now, and have you verified the odometer is reasonably accurate?

I kinda doubt that you can get any better mileage out of a 4x4 351 with *any* gears.