I just installed a differential with 342:1 gear ratio with 31 spline axles (originally 308:1 with 28 splines) and i know i need to change the speedo driven gear but i just dont know which one to use or how do i calculate it (regular 14" wheels). Where is the best place to purchase it? I could use some help on this one. Thank you in advance.

 

http://speedometersolutions.com/

 

My guess would be you'll want a 20 or 21 tooth driven gear. Based on the chart.

misc.jpg

 

Thank you guys for the info, i called Speedometersolutions.com and they were very helpful. They told me to (1) measure the exact eight of the tire, (2) take the presently installed driven gear and count the teeth & finally mark tooth of drive gear than count all teeth of drive gear. I was told to call them back with the results after which they will recommend a driven gear for it (i am guessing 20 or 21 at this point). Hoops, i didnt realize that my manual shop had this information as well. Thanks guys!