Which Gearing do i have

[Beersnob]

It's not the most accurate way, but you can jack up the rear and spin the rear tires together and count the revolutions of the tires vs the revolutions of the driveshaft. Tires doing one full rotation vs driveshaft doing just over three is normally 3.07, just over 3 1/2 is usually 3.55, just under 3 3/4 is 3.73 and over 4 is 4.10. Again, it's not the most accurate as you've got driveline slack and open differentials to deal with.