Speedometer Gear Selection Calculator

Drive Gear Teeth:

Axle Ratio:

Tire Height (Inches):

Result

Required Driven Gear Teeth:


Firebird Speedometer Gear Application Chart

3 Speed Manual4 Speed Manual 
3spdman13spdman24spdman14spdman2 
2 speed automatic

 

M38

 

M40

 

2spdauto12spdauto2350auto1400auto1400auto2
   

 

 


Typical 14" Tire Sizes

P215/60R1424.1
P225/60R1424.5
P235/60R1425.0
P205/70R1425.2
E70-1425.7
P215/70R1425.8
F70-1426.2
P225/70R1426.3

 

Some popular transmission ratios

Transmission1st2nd3rd4th5th6thRevShift RPM Multiplier
        1-22-33-4
ST200 1.761.00 1.82.568  
Turbo 3502.521.521.001.94 .603.658 
Turbo 4002.481.481.002.08.597.676 
200-4R2.741.571.00.672.29.573.637.670
700R43.061.621.00.702.29.529.617.700
           
Saginaw 3 speed iron2.851.681.00    .589.595 
Saginaw 3 speed iron2.541.501.00    .591.667 
Saginaw 3 speed iron 3.111.841.00    .592.543 
Saginaw 3 speed iron3.501.891.00    .540.529 
Muncie 3 speed iron3.001.751.00    .583.571 
Muncie 3 speed iron2.411.571.00    .651.637 
Saginaw 4 speed iron2.842.011.351.00   .708.672.741
Saginaw 4 speed iron V82.541.801.441.00   .709.800.694
Saginaw 4 speed iron 6 cyl3.112.201.471.00   .707.668.680
Saginaw 4 speed iron3.502.471.651.00   .706.668.606
Muncie M20 (Wide) 4sp '63-'652.561.911.481.00   .746.775.676
Muncie M20 (Wide) 4sp '66-'742.521.881.461.002.59.746.777.685
Muncie M21 (Close) 4sp '63-'742.201.641.281.002.27.745.780.781
Muncie M21W (Close)2.521.731.351.00   .687.780.741
Muncie M21Y (Close)2.201.511.000.86   .686.662.86
Muncie M22 4sp '65-'742.201.641.281.00   .745.780.781
Borg Warner T-10 Wide 4sp early2.561.911.481.002.64.746.775.676
Borg Warner T-10 Close 4sp early2.201.661.311.002.26.755.789.763
Borg Warner Wide 4sp '74 up2.641.751.341.002.55.663.766.746
Borg Warner Close 4sp '74 up2.431.611.231.002.35.663.764.813

Shift RPM Multiplier:  Multiply your desired shift point RPM by the multiplier to find the engine RPM after the shift.

Please notify Webmaster of any inaccuracies on this chart.

See these tech articles for more information:

http://www.mickeythompsontires.com/tech_diameter_rollout.html

http://www.mickeythompsontires.com/tech_backspacing.html

http://www.mickeythompsontires.com/tech_metric_conversion.html