[Ackattack]

I put in a 700r4 when I put in my TPI 350 so I don't know its affect on gas mileage alone.

But with the 3.08 gears the RPMs were way too low and it was lugging the crap out of the engine on the highway at 60. I switched to 3.73 gears and the truck drives a lot better all around and I picked up about a 1.5 mpg.