I've been reading some posts and need some help.
I found this great link from HwyStarJoe on GM rearend gears.
http://www.novaresource.org/axle.htm

'68 Camaro Conv., 327, 2-speed powerglide..
I'm trying to figure-out what gears I have in this rear end, (without pulling the cover and counting teeth).

Numbers on the axle are BP0626G
BP = 2.73 open
06 = May
26 = 26th
G = Detriot Gear and Axle

Ok, I put the rear axle on jack stands and put a peice of tape on my wheel to mark it's rotation.
I then spun the drive shaft 1.33 time to the tires 1 rotation.

..so it appears to me that ratio to 1.33???????
WTF
I would believe the 2.73,
but what am I doing wrong with this rotation test?
Shouldn't spinning the tires once, rotate the drive shaft 2.73 turns?

Ghostbuster

On an open rear, jack up 1 rear tire and spin it exactly 2 times to figure your ratio. (or just multiply what you came up with by 2 :D )

On a posi rear you want both tires off the ground and only do 1 revolution.

Mark

..that makes my numbers come out right, but I'm still confused..
..so my wheel spins 2x, to the driveshaft spinning 2.73 times.

My HS math teacher told me that would be 2 : 2.73 ratio?

since you have an open rear, when you spin 1 tire, the other is actually spinning backwards due to the spider geasrs in the diff, watch it and see.

1.33 x 2 = 2.66:1, close enough to 2.73, just like it says on the tag.

doh!
well, that makes sense now..

(lesson - never ask a math teacher a car question..)

Thanks JimM & Mark..