Replacing my differential with one that has different gear ratio's and wondering which one to purchase. I have 3:23 to 1, M-20 4 speed transmission (don't know the amount of teeth of plastic gear inside the transmission) 20 teeth speedo gear (Blue) wheels are 26" total diameter but if measured from center to outer edge it's only 12 1/2". Do i go 19 or 20 teeth? Were can i get one made in the USA? Thank you in advance.

 

https://www.tciauto.com/speedometer-gear-calculator

Hopefully this helps. You need to know the gear ratio, tire diameter, and either the drive or drive gear tooth count. This will calculate the other gear needed. Play around with different tooth count, you want to come up with a combination that has the closest whole number. You can’t have a gear with 19.5 teeth! The closer to a whole number, the more accurate the speedo.

 

Everything that i know is listed in the thread. Gear ratio is 3:23 to 1, M-20 4 speed transmission, wheels w/tires are 26" diameter but if measured from center to edge of tires it's 12 1/2" the only thing i do not know is the tooth count inside the transmission (originally 3:23 to 1 M-20 4 speed).