Speedometer gear

[Lake Martin John]

GOOD DAY TO ALL! I recently purchased a '65 Mustang sedan with automatic tranny and a 289 V8. The speedometer reads 8mph high at highway speeds. At 55, speedo reads 62. Should I replace the transmission gear with one that has more teeth, or less teeth? MUCH THANKS in advance!

 

[dennis112]

GOOD DAY TO ALL! I recently purchased a '65 Mustang sedan with automatic tranny and a 289 V8. The speedometer reads 8mph high at highway speeds. At 55, speedo reads 62. Should I replace the transmission gear with one that has more teeth, or less teeth? MUCH THANKS in advance!

Slowing the speedo down will take more teeth on the gear at the end of the cable. My rule of thumb is that 1 tooth is around 2 1/2 MPH@55mph so a gear with 3 more teeth should have you in the ballpark (as long as you maintain the same rear tire diameter.)

 

[Lake Martin John]

Slowing the speedo down will take more teeth on the gear at the end of the cable. My rule of thumb is that 1 tooth is around 2 1/2 MPH@55mph so a gear with 3 more teeth should have you in the ballpark (as long as you maintain the same rear tire diameter.)

MUCH THNKS my friend! You and the others on this site ar so valuable to me, you are appreciated!!