[Rev]

Just raise one rear wheel off the ground and put the tranny in neutral. If you can turn the wheel that's off the ground, then you probably have an open (one legger) differential. If you can't urn it by hand then you have a posi (Traction-Lock).

Assuming you can turn the wheel that's off the ground, make a chalk mark on the tire and on the drive shaft. make one complete turn of the wheel and count the number of revolutions that the drive shaft makes. That number divided by 2 is the axle ratio. For example, 5.6 turns of the drive shaft would mean 2.80.

If it's a posi, then jack both wheels up, do the same thing, but don't divide by 2. As in the previous example, 1 wheel revolution might make 2.8 drive shaft revolutions, meaning a 2.80.

Rev