Expert: Dan Liddy - 11/17/2006

Question
Danny,
My question is not specifically about auto racing but it does involve rear end gearing... My vehicle is an F250 Diesel (Autotrans w OD) with 3.73:1 rear... (This is a non towing vehicle) I travel mostly on the interstate and i need to increase the MPG... Considering the torque curve of the 7.3 L diesel what gear replacement do you suggest? Are there a limited number of off the shelf replacements?

Answer
Hey phil:

You would have to cousult your Ford dealer as to which rear end ratios are available.

Sinci you are not towing anything you can make a significant change in the fuel consumption.  If you are now getting around 18 MPG, a change to a 3.50:1 rear ratio would gain you about 9 % , or  about 19.5 MPG.  Taken a step further, a 3.37:1 rear would gain you another percentage point , or 19.8 MPG.  In this case, I think I would stay with the 3.50 rear for the little bit of added low end pulling power.

Another thing most people overlook is weight. How much extra junk are you hauling around with you every day. It takes FUEL to move that 2 ton tool box, the topper, all the extra toys us guys have to have with us.

Those are my thoughts, hope they help !

Dan Liddy
Sarasota, Florida