need another gear!!!

[Landpimp]

from your location, I would guess it has the 4:10;s

3.7's and 33's is a very fine combo, I run this is my 82fj40 and love it,

 

[Fast Eddy]

Keep in mind that both tires have to spin at the same time. If one spins faster your numbers will be off.

If they're both off the ground and they don't spin the same you have a brake or bearing problem. Mark 'em both, I guess.

Just leave it on the ground and roll it straight one full wheel turn. If the driveline rotates just over four times it would be 4.10 under the four turns probably 3.70.

It's harder to determine the driveline rotation than a wheel rotation.

 

[Mace]

If they're both off the ground and they don't spin the same you have a brake or bearing problem. Mark 'em both, I guess.

Just clarifying..

Then there is the option of the other tire spinning backwards

 

[Living in the Past]

It's harder to determine the driveline rotation than a wheel rotation.

Not real hard to do. Mark the wheel at the bottom and do the same to the driveline. White would probably work best for the driveline so it's easier to see. Have someone watch which way the driveline is rotating. Once you push the vehicle one full wheel turn check to see if the driveline is coming up on the bottom or just past. If it's short then 3.70, past then 4.10. As for a open diff I've had the opposite wheel spin just as many time as not. If the rear and pinion pre load is tight and same with bearing in the back of the transfer with stock size wheel and tires it's a toss up which spins. I guess I just always look at these as a simple utility vehicles and work on them the same way. Can't see any reason to put it up on jack stands when I can figure it out before I dig out a floor jack and jack stand.