currently, we have a 2002 e250 with a 5.4 and 4 speed transmission. i believe the gears are 3.73 in the rear. we get about 15mpg to a tank average, loaded with about 1000lbs of tools. we are looking at a 2011 e350 with the 5.4 and 5 speed transmission. it has 4.10 gears in the rear and a knapheide utility box on the back(about 90" wide). i figure it would probably get a little less because of the added weight and wind resistance, but im not sure if the 5th gear will even out the 4.10 gears to the 3.73 in the e250. would it see better city milage and less hwy milage?we average about 20k mostly hwy miles a year, so id like to be close to 15 average. anyone have any experience with a setup similar to the e350 i described? any help is appreciated

 

The 5th gear will not even out the 4.10 ratio. 4th gear in the four speed transmission is 0.71:1, which happens to be exactly the same as 5th gear in the five speed. The engine in the 2011 will be turning 10% faster at all speeds.

 

thats exactly what i was looking for. is it possible to swap a set of 3.7 gears in the rear end of the 350 axle and keep the same limited slip diff? on this model, the hubs stick out past the rim about 3", if that helps to determine what it is. thanks for the help.