The car is a 1970 Rallye 350 4 speed. Today, we wanted to verify the rear end ratio. The rear end has the posi tag. I did not want to scrape off the undercoating to find the axle code. Here is what we did:

We secured the car on Jack Stands
We turned the passenger rear tire forward. We noticed the driver side turned forward as well.
We turned the passenger rear tire backward. We noticed the driver side turned backward as well.

We marked the drive shaft with a piece of tape
We marked the passenger rear tire with a piece of tape
We turned the passenger rear tire ONE FULL turn forward while counting the number of revolution of the drive shaft.
We counted just under just under 4 drive shaft turns for 1 tire revolution (~3.9 turns)

Did we do this correctly? So does that mean we have somewhere around a 3:91 gear? If not, what should we have done differently? Thanks

 

You did it right!

 

Now Go Use that DIFF.