What gear ratio do I have?

[Dreamcar]

I've changed the subject line as I realised it may be misleading...

Right now, the rear-end from my 69 383-4 is sitting in a corner of my garage and will need a once-over and potential rebuild. Is there any way of knowing approximately what gear ratio is in it right now by spinning it by hand and whether or not it's a sure-grip? It's a 489 case and the car came with the A35 Tow Package. 

[Dreamcar]

I thought I read somewhere that by spinning the yoke and counting the rotations at the wheel it would give you an approximate idea. Is this true?

[70 sublime]

If you turn the wheel 10 times then count how many times the yoke turns will tell you

wheel 10 times and yoke 32 and a bit is 3.23

wheel 10 times and yoke 27 and half is 2.76

If you are lucky you might find a small metal tag sticking out from under one of the bolts that hold the center section into the rear end with the numbers stamped on it

[Dreamcar]

Thanks!

[chargd72]

Or you can divide those number by 10.  Spin wheel 1 time and yoke spins 3.2 times you have 3.23 etc.

[John_Kunkel]

Turn one drum/axle to make sure the rear end isn't locked up. When turning one drum, if the other drum turns in the same direction it's Sure-Grip, if not it's an open differential.

With Sure-Grip, simply turn either drum one full turn and count the turns of the pinion yoke, the number of turns of the pinion is your ratio. (for example, 3 1/4 turns is 3.23 axle ratio)

With an open differential, hold one drum from turning and turn the other drum two full turns and count the turns of the pinion.

[Dreamcar]

So when I got home, I unburried the diff laying in the corner and turns out it still has the small tag with the ratio written on it...3.23, but non-suregrip.