How to check rear axle

[Flashflood]

My rear axle on my 91 sport looks rather clean for maybe being a almost 30 axle even compared to a 99 back axle I'm wondering how to check the back axle code without doing the turning of it cause I've tried to do that and my back axle wouldn't turn

 

[massacre]

I think there might be an axle code on the door sticker?

 

[Flashflood]

I think there might be an axle code on the door sticker?

Well I'm just checking to see if it hasn't been geared up from it's stock axle which I would already know 3.55

 

[410Fortune]

two ways to check:
open diff cover and count teeth
or rotate tire and count rotations of the pinion
Jack up both rear tires, put truck in N, make a mark on the pinion and tire. Spin the tire one time around.....of the pinion only moves 1.75 turns then turn the tire twice around and count the number of turns on the pinion

So the way this works is with a limited slip or locker you only have to turn the tire one full revolution and your pinion will turn 3.5 times (3.55) or 3.75 times (3.73) or just past 4 times (4.10) or 4.5 times (4.56) almost 5 times is 4.88 and over 5 is 5.13 gears.
If you have an open diff, (no limited slip no locker) then rotate the tire twice around.......

This is a fail proof method.
If you cannot turn the tire then you have dragging brakes that should be fixed