If you still have the cover off, just count the number of teeth on the ring gear and the pinion gear, then divide the ring gear count by the pinion count. If you already put the cover back on, just turn one wheel 2 revolutions while counting the number of driveshaft revolutions. 3 driveshaft revolutions = 3.07:1, 3 3/4 revs = 3.73:1, etc. If it's a posi-trac then you will have to turn both wheels a full revolution. Hope that helps.
