If you opt to jack up one wheel and count driveshaft turns, remember that the spider gears will double wheel speed. For instance, if it takes 2 1/2 turns of the driveshaft to get one wheel rotation, the axle ratio is actually 5:1. Be sure and double the number of driveshaft turns to figure the actual ring & pinion ratio, or keep turning the driveshaft until you get two turns of the wheel.
Jerry