How can I go about determining the gear ratio in my JK currently? I am sure the window sticker said...but I cannot seem to locate it.

 

Axle ratio? If so:

If you want to know for sure, and remove all doubt, do this:

Chock the right rear tire, fore and aft.
Put the transmission in neutral.
Emergency brake off.
Jack the left rear tire off the ground.
Put a jack stand under the frame, just in case the jack fails (had to add this).
Put an index mark on the aft end of the drive shaft, visible from the left rear wheel.
Put an index mark on the left rear tire at the 6 o'clock position.
Rotate the left rear tire 2 complete revolutions while counting how many times the index mark on the drive shaft passes its original position.
That number will be your axle ratio.
Remove jackstand and lower jack.
Put transmission in gear and/or apply emergency brake.
Remove chocks.
If you have limited slip, jack up both rear wheels and rotate one revolution, making sure both tires rotate equally.

If the driveshaft rotated almost 3 1/4 turns, you have 3.21
If the driveshaft rotated almost 3 3/4 turns, you have 3.73
If the driveshaft rotated a little over 4 turns, you have 4.10

 

This is what I did

 

Just a quick comment on this. I went to the dealer, they printed off a " build sheet" that said 3.21s on my rig. Just to be sure I sent an email to JEEP. They emailed me a build sheet that said 3.73s. Maybe if I can find someone else to email and ask they will go up to 4.10s???? Just my 2 cents

 

That is why my advice on this subject ALWAYS starts out with "If you want to know for sure, and remove all doubt, do this:"
Build sheets are fun to have, but when you are making decisions, you need the correct facts, not some extrapolation from a source thousands of miles away.