Mopar Speedometer Pinion Numbers

Tire Overall Diameter

AXLE RATIO

 24" 26" 28" 30"
2.76 2538930 2538928 2538926 2538924
2.94 2538932 2538930 2538928 2538926
3.21 2538935 2538933 2838931 2838929
3.55 2538939 2538936 2538933 2538931
3.91 2538943 2538940 2538937 2538935
4.10 2538945 2538942 2538939 2538936
4.30 2538944 2538941 2538938
4.56 2538945 2538943 2538940

Please note: these numbers are for the standard style pinion gear
also last two numbers are the number of teeth, 2538945 = 45 teeth

How to Calculate tire diameter: Example 265/60/15

265mm/25.4mm = 10.43 Inches Section Width

10.43 in. X 60% = 6.25 in. Side Wall thickness

6.25 in X 2 = 12.5 in Total Side wall height

12.5 " + 15" (rim Size) = 27.5" Diameter

So with this Tire size and 3.55 Gears, I would use 35 Tooth Speedometer gear.