Determining rear axle ratio
I wanted to know what my ‘68 Tempest had for a rear axle ratio, I’m thinking about using it for commuting and am wondering what I could do to improve mileage. First I jacked up one side of the rear axle (if you have positraction you’ll need both wheels off the ground), then put a chalk mark on the drive shaft and the differential.
Then I put a mark on the tire where it lined up with a crack in pavement.
Next you just rotate the tire, and count how many times the driveshaft rotates and the tire rotates until both marks line up similtaneously. It takes a lot of turns, I kept tally on the sidewalk with a piece of chalk.
It took 32 turns of the driveshaft and 25 turns of the wheel before the marks lined up again. 32/25=1.28, but since only one wheel was turning I have to multiply by 2 to get 2.56 for the actual ratio. I guess I’ll have to look elsewhere for gas mileage improvements.
