Speedometer gear selection guide

[Mrmopartech]

Speedometer Gear Selection Guide
Overall Tire Diameter

Axle Ratio
24" 26" 28" 30"
2.76 2538930(Yellow) 2538928(White) 2538926(Red) 2538924(White)
2.94 2538932(Black) 2538930(Yellow) 2538928(White) 2538926(Red)
3.21 2538935(Orange) 2538933(Yellow) 2838931(Green) 2838929(Black)
3.55 2538939(Green) 2538936(Red) 2538933(Yellow) 2538931(Green)
3.91 2538943(Blue) 2538940(Orange) 2538937(White) 2538935(Orange)
4.10 2538945(Yellow) 2538942(White) 2538939(Green) 2538936(Red)
4.30 2538944(Black) 2538941(Red) 2538938(Blue)
4.56 2538945(Yellow) 2538943(Blue) 2538940(Orange)


Please Note: These part numbers are for the standard style pinion gear. The last two numbers of the part number is the number of teeth for the gear (Example 2538943 = 43 teeth).

Here is an example on how to calculate the wheel diameter to select a speedometer gear to use with the desired ring/pinion gear.

Tire Size: 245/60/15

245mm/25.4mm = 9.64 Inches Section Width

9.64 in. X 60% = 5.79 in. Side Wall Thickness

5.79 in. X 2 = 11.57 in. Total Side wall height

11.57 in. + 15 in. (Rim Size) = 26.6 in. Diameter

So with this Tire Size and 3.91 Gears, I would use a 40 Tooth Speedometer gear.

 

[onehellofadart]

Good to know! Thank you!!!

 

[Mopar318Guy]

well i might go bigger. so i could go with a 37 tooth?? incase i do get the 15s with 275/60s and whoever said just get an electric speedo thats possible too