If you changed to 2.56 gears (not sure they make them) you would lose mpg around town and most likely even combination city and hwy. If you only drive freeways you might gain a bit, but your bottom end would really suck.mopar89ram said:I have a o1 DAkota, regular cab, with a 3.9Lv6. It has a auto trans, with 16 rims, stock. I figured out with my truck, that when the gas light comes on it has 1/8 of a tank left. It has a 22 gallon tank. I cam up with 16 mpg. I only get 320 on a tank. Part of my problem is that it has a 8 1/4 rear with 3:55. Can i enstall 2:56 gears? Also what would be the cost for the gears? Any information would be greatly appreciated.