John Dirks

I just jacked up the rear end of my 76 coupe to check the gear ratio.
I put the TH350 in neutral, chalked the drive shaft, and with both wheels in the air turned one wheel one complete revolution and counted 3 turns of the drive shaft (I gather this means 3.08 ratio).
What I noticed however was when I turned one wheel forwards (as if the car was going forward) the other wheel was turning in the same direction.
And if I turned the wheel backwards, the other wheel did not turn at all.
Does this sound like a posi rear end?
I thought I had heard that if both wheels were in the air, and you turned one wheel forwards, the other wheel turned in the opposite direction????
Can anyone shed some light on the subject?
Thanks.

Ron 75 L48

John, you should have a red tag on the filler plug warning you to make sure that you add the posi additive if it is a positraction. Also according to my facts book it says that the '76 3:08 has a positraction stamped code of OA on the underside of the differential where the flange cover attaches.

:flag
Ron

Gordonm

If both wheels go in the same directio nit is a posi. One forward one backward is an open rear. You have posi

Jughead

All C-3's from 1970+ are posi units according to the Black Book. In the C-4's it might be called a limited slip.

John Dirks

Thanks guys, you have given me peace of mind.
I looked for the stamped letters on the diff but because they are worn a bit the stamp letters looked like "OK" but I guess they must be OA.
Thanks.