How do i tell what gears are in the rear end?

[barryTA]

just got a rear from the junk yard they say its 3.42 gears but i need to know for sure how do i tell where do i look for the numbers?

[Danger731]

I know old school had the numbers on the drivers side of the axel facing down.

[2001NBMZ28]

GM usually stamps it on the edge of the ring gear. Just count the teeth on the ring and pinion and do the math. For example:

42 tooth ring gear, 13 tooth pinion gear - 42/13 = 3.23

[bigrondownhiller]

You could also turn the axles and count how many times the pinion turns in relation to the axles. If the pinion turns 3 and a half for one revolution of the axle you have 3.42.