View Full Version : Rear End Gear Ratio for Mileage

03-29-2006, 05:36 PM
I think I about have all the parts together to convert my '63 Champ pickup to a GM 700R4 automatic overdrive. I hope to be able to post pictures on this media as we progress.

My question today is what would be the best rear-end gear ratio for the optimum in fuel mileage. Presently I have a twin traction 4.09 rearend on the truck. I won't be hauling anything "super heavy", like a truck load of bricks or lead pipe! So I don't need to worry about that... and of course this conversion would be after I try the truck with the 4.09 and overdrive. I know if I go with too low (numerically) a gear ratio it will be as bad as too high.

Any suggestions?

Laisez le bon temps roulez avec un Studebaker

03-29-2006, 07:13 PM
I would suggest trying it out with the 4.09 and going from there, you
are going to end up with an impressive pulling grunt. The 700 has a
3:1 first gear, which will be nice for towing and take off. The OD is
a .8:1. Once you have it together and calculate your mileage, you can
figure out what to do then.


1963 Studebaker Avanti (http://hometown.aol.com/sbca96/images/63avanti.jpg), 102,000, custom made brake brackets to mount 1998 Mustang GT 4 wheel disc brakes (soon to get 13" Cobra front brakes, 2003 Mustang Cobra 17" wheels, GM altenator, will be getting : 97 Camaro Z28 tan leather seats, 97 Camaro Z28 T-56 6-speed trans, Ported 'R3' style Avanti heads with stainless full flow valves, 'R3' 276 duration cam w/chrysler solid lifters, shortened push rods, aluminum cam gear, Edelbrock AFB Carb, GM HEI distributor, 8.8mm plug wires, waiting in the garage.