What's the best way to determine gear ratio in axles?

[willig2]

Hello all, I recently acquired a 1984 4 Runner. The seller advised that 4.88 gears were installed in the axles. With 31's, I figured it would be much different from the stock 4.10 which I have driven. What is the best way to check this? No stamp or color code that I can find. I researched it and have found there are several different ways to determine this. Any help is greatly appreciated.

 

[bamatoy]

Count the driveshaft rotations to 1 complete turn of the tire. Should be real close to 5 turns of the driveshaft to 1 tire rotation