National Drivetrain - rear end parts
  Vehicle Specific  Non-Vehicle Specific
Clearances & Special Offers
Spider Gear Set
Limited Slip Posi
Ring and Pinion Gearset

Beginner and Intermediate Gear Ratio Calculators

NOTE: Advanced/Racing Calculators Located Bottom Of This Page

 

Compare Gear Ratio and Tire Diameter Combinations
   
Tire Diameter(inches)  
Gear Ratio  
Miles Per Hour    
Overdrive %(none=0)    
RPM @ 70  MPH-In Drive  
RPM @ 70   MPH-In Overdrive  
 
Metric Tire Size Conversion
Height inches
Width inches
 
Gear Ratio
Ratio
Recommended Gear Ratio - Tire Size Change
Enter Current Gear Ratio  
Enter Original Tire Size  
Enter New Tire Size  
Ideal Calibrated Ratio  
 
Acceptable Gear Ratio Target Range
 
Recommended Gear Ratio - RPM Change
**Based on same speed that RPM is being calibrated from
Enter Current Gear Ratio  
Enter Current RPM  
Enter New Desired RPM  
Ideal Calibrated Ratio  
 
Acceptable Gear Ratio Target Range

 

 

 

Advanced/Racing Gear Ratio Calculators

 

Tire Diameter #1(in.)
Gear Ratio #1
Tire Diameter #2(in.)
Gear Ratio #2
Overdrive % (none=0)
Target MPH
Redline
Ft/Lb Torque @ Pinion Yoke
 
RPM @140   MPH-In Drive
RPM @ 140   MPH-In Overdrive
Top Speed @ 6500   RPM-In Drive
Top Speed @ 6500   RPM-In Overdrive
Axle Shaft Torque Output

3 Speed 1st
  2nd
  3rd
4 Speed 1st
No Overdrive 2nd
  3rd
  4th
4 Speed 1st
Overdrive 2nd
  3rd
  4th
5 Speed 1st
  2nd
  3rd
  4th
  5th
6 Speed 1st
  2nd
  3rd
  4th
  5th
  6th


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