Technical Determing banjo rear ratio

With a banjo rear, it is tough to count drive shaft turns to find out what gear is installed. I finally had an idea. I took the top of the trans and marked one tooth of the 1/R gear with a dab of white paint. I used chalk to mark the tire and the floor. I jacked up the tire and rotated it two turns.
A 4.11 would put the tooth mark right on top, A 3.78 would have it at 3 or 9 o'clock. A 3.54 would have the tooth on the bottom. I have a 3.78.
Mystery solved. It had a 21 tooth turtle so that was wrong. A 18 tooth seemed wrong as well.

 

Or just look at the stamped rib.

39-9 for 4.33
37-9 for 4.11
34-9 for 3.78
39-11 for 3.54

 

And that would tell me something????
Mine was stamped 37-9 (4.11) at the factory but my test found that has been replaced with a 3.78. That was the purpose of the test as I thought I was going faster than a 4.11 would allow. The turtle was a 21 (4.11). I had replaced it with a 18 and that seemed not right either. I need to put a 19 on there.

 

I know a rearend or two that have been changed and didn't get restamped. Never trust what you can't prove.