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  • 1965 - 1973 Classic Mustangs -General/Talk-
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Speedometer gear

  • Thread starter Thread starter Lake Martin John
  • Start date Start date Apr 18, 2019

Lake Martin John

Member
Feb 25, 2019
18
2
13
Lake Martin, Alabama
Apr 18, 2019
#1
  • Apr 18, 2019
  • #1
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

15 Year Member
May 15, 2005
1,561
36
79
Amish Wonderland of Central PA.
Apr 18, 2019
#2
  • Apr 18, 2019
  • #2
Lake Martin John said:
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!
Click to expand...


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

Member
Feb 25, 2019
18
2
13
Lake Martin, Alabama
Apr 18, 2019
#3
  • Apr 18, 2019
  • #3
dennis112 said:
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.)
Click to expand...
MUCH THNKS my friend! You and the others on this site ar so valuable to me, you are appreciated!!
 
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