Speedometer Gear Selection

[61RANCHERO]

I am swapping rear ends from a 4.0 rear ratio to a 3.5 ratio, I have a Fordomatic 2-speed and need to know what speedometer drive gear to order.... How many teeth?

Thanks!!

Glenn

[pbrown]

Here is a good calculator. You will probably need a 20 tooth gear.

http://www.tciauto.com/Products/TechInfo/speedo_gears.asp