Testing Front Diff Gear Ratio

Hey guys.
I started tearing down the front end today for my 4wd swap.
As I grab the front diff to bolt it in... I feel a sense of uncertainty.
I bought the diff from someone parting out a 4runner off craigslist.
He gave me the indoor sticker info and according to several documents its a 4.10.

I dont necessarily want to trust the guy that sold it to me nor the online articles about identifying the numbers on the sticker.

So with the diff out of the car I marked the output flange on the diff. I marked the silver ring on the inside of the non A.D.D output tube and spun the flange 4 times. The ring on the output tube where the cv goes into had about .8 turns for the 4 turns at the flange.
Now... I don't like the method I used. Is there a better method? The diff is out of the car and has no cvs plugged into it.
I don't know how to split the case (seems like a pain).
I'm worried this might be a 3.73? I didnt get a full 1 turn to 4 ouput flange turns.

Thanks

 

Easy, buy mine and the rear gears that are 4.56 and don't worry about regearing in the future! haha

Okay, Well it is a pain if you do not have CV's. The problem is that when spinning the flange the outputs for each side are not necessarily spinning at the same rate. (Imagine that only the driver side is spinning for example and the passenger side is not)

Try spinning both sides of the differential and watching the flange turn. This should give you a more precise estimate of what it is.