Gearing in my dirt car
 

I need to know the gearing in my circle track dirt car. I have a three speed saganal with a 390 rear in the car. Can I turn the the driveshaft in 2nd gear (that is the gear I run) and do some kind of counting of revolutions to the back wheels? If so, how do I do it?

Turn the input shaft in each gear and count the input revolutions to what it takes to turn the out put shaft one revolution. This will give you a ratio for each gear, if it takes 3.75 turns on the input shaft for one revolution in the out put you have 3.75 to one ratio. etc... if you are only interested in the final gear ratio you can leave the drive shaft in and count the inputs to one revolution at the axle. Or multiply the 3.90 by the trans gear ratio if you prefer.

Thank You!!