I'm still not sure what the ratio is, however I'm thinking of lifting the rear end and marking the drive line and turn the rear tires to count revolutions, etc. to figure it out.
It's a lot simpler to just mark a tire and the driveshaft, and have someone drive the truck straight forward or back one turn of the wheel while you count the turns of the driveshaft. There's no involvement of the differential gears that way, and you'll get a much more accurate count of the pinion gear revolutions.
Jerry