My 67 Bird was originally six cylinder automatic, now 400 4-speed. The differential is non-posi. When I jack up one wheel and turn it one complete revolution, the drive shaft turns about 3 and one-fourth turns.
What ratio do I have?

i belive the original on a 1bbl 4.1l OHC6 was a 2.73 (i might be wrong) but it was for the 2 speed tranny

you may wanna go up to a 3.42 for cruising or 3.55 if you like higher RPMs

1 divided by 3.25 is about .308. so 3.08. 2.73 would be about 3 and 3/4 turn.

That doesn't make sense. The lower (numerically) the gearing is, it should take fewer engine revolutions to turn the wheel 1 time. 3.25 turns of the driveline to 1 turn of the wheel is probably a 3.23 rear.

Why does the number 3.23 pop up in my mind when thinking 67 BOP?

Tim, you beat me by 5 seconds!

Yep. I was using fuzzy math. LOL

I have to disagree ... in principle.

For a non-posi rear end, if you jack up one wheel only and turn it one revolution, the number of driveshaft turns will be half of the ratio.

What you may have counted was the number of times the u-joint bearing came into view, which makes your rear end a 3.08.

Jim was right, but he just guessed lucky. Fuzzy math works mysterious ways.

To get the right answer, jack up the one wheel and spin it TWICE while counting the number of turns of the driveshaft. Mark the companion flange and the housing with white-out to make this easier.

That's why they call it fuzzy. What do they say, "Better to be lucky than good"! Either way it's good to be right when they pile on you.

Kpral,
Keep watching, you will catch me again, no doubt. :p If you're never wrong then you are dead.

Thanks, everyone.
It's a 3.23 Open.
I also found the XF on the axel housing.

Someone must have switched the gears.