Ive changed tires / gearing and now my speedometer is reading incorrectly. Help?
See Matt’s speedometer gear chart at http://w3.one.net/~mhaas/techinfo/gearteeth.html another note by Matt: The only problem you may run into changing transmissions is the drive gear. In the 60’s, AMC had three (7, 8, or 9 teeth). Assuming the number of teeth on the drive gear is the same, you shouldn’t have any problems. The gear is on the output shaft and it doesn’t matter what type of transmission is already there. I do have gear charts for 66-69 on my web site in the Technical Information section. To figure out which gears to use, you need to know the axle speed at 60 mph. To get this, divide 5280 by the circumference of your tire to get axle rotations per mile (which is a constant). Use this number and your rear gear ratio to get the proper gears to use. If that doesn’t work for you (like when you have an aftermarket gear ratio or very tall tires), you’ll need to calculate the driveshaft speed at 60 mph and then divide that number by 1000 (which is how fast the speedometer cable s
