What rear end gears should i put in my truck?

Question

I have a 1969 chevy truck that has a 3 speed transmission and i want to change the rear end gears to better the mileage because its geared really low. i would mostly do highway driving at about 55 to 60 mph. what ratio should i get for the rear end to get the best mileage possible on the highway.

Answer 1

I would say a 373 would be your best bet

Answer 2

It depends.  I would shoot for 1500 rpm or a bit less at 60 mph.  To calculate the rear end ratio to achieve this, you need to know the diameter of your rear tires.

Changing the rear gears like this will have a major negative impact on acceleration.  You may want to look into a wide ratio four, five or six speed transmission.

For highway speeds (45 mph and up); the one biggest thing that you can do to a pickup truck to improve fuel economy is bed cover.

Other factors that can improve fuel economy:

* make the truck as low as practical.

* use as narrow a tire as practical.

Answer 3

look for a mid to low "3" series gear. say a 3.55 or lower. be cautious of going to low. some vehicles are equipped with a low gear to compensate for low torque