National Drivetrain - rear end parts

Clearances & Special Offers

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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