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Willys MB/Ford GPW Speed Calculator

 

Instructions: The calculator is preloaded with some typical values. To see the speed with other values, click buttons on the lists of common values provided, and watch the speed change. Or fill-in numbers directly in the blanks, and when the cursor leaves the input box, the speed will be recalculated.

Tire Size

Axle
Gears 		Transfer
Case 		Trans Overdrive Calculation

27″
28″^
29″
30″
31″
32″
33″
34″
35″

Spicer 23-2
4.88:1 (44/9)*

Spicer 18
–27 tooth*

normal
low

Spicer 18
–26 tooth

normal
low

T84J*
R
1st
2nd
3rd
Warn/Saturn#
normal
overdrive
Engine RPM
Transmission Ratio : 1
Overdrive Ratio : 1
Transfer Case Ratio : 1
Ring & Pinion Ratio : 1
Tire Diameter inches
Total Gear Ratio : 1
Speed MPH
* Standard WW2 jeep features
^ Standard WW2 jeep tire diameter – 6.00×16
# Non-standard option, if no OD leave blank or select “normal”

This calculator is based on the work of Richard Grover, see Willys Utility Vehicle Speed Calculator for calculator on post-war jeeps.