PartsMike® Online

We have put together this handy little calculator to help figure out the correct speedometer gear needed to match your drivetrain and tire combination. All you need to know is:

1. The number of teeth on the speedometer "drive" gear (This is the one on the output shaft in the transfer case. 13 is a very common tooth count for Jeep, Dodge, and Atlas transfer cases which is why we have set it as the default. The calculator will take any value between 6 and 22)
2. The axle gear ratio
3. The Tire diameter
4. The speedometer revolutions per mile. (The speedometer revs per mile number can be found somewhere on the speedometer and will be something like 940, 970, 1000, etc. For Jeep it is 970 so we have set that as the default but you can input the appropriate number for your speedometer)Plug those numbers in below and the correct tooth count for the "driven" gear (the one that meshes with the "drive" gear and the speedometer cable) will appear.
   
   

   Speedometer Revs per Mile: 
   (970 is the standard value for Jeep vehicles)
   
   # of Drive Teeth: (6-22)      
   
   Axle Gear Ratio:                 
   
   Tire Diameter:                    
   
           
   
   # of Driven Teeth: