While you may think you know your Jeep's gear ratios based off its year and/or differential type, if the vehicle was purchased used then someone may have changed them at some point in the past. So an easy way to determine your actual gear ratio is to check the tag attached to the differential cover by the cover bolts. On the tag there should be some numbering such as 3.54 or 3.73, either of those numbers will give you the stock axle ratio. To verify, or to see if that ratio has changed, you can jack up the rear axle and support it with jack stands. With the transmission in neutral, rotate the rear driveshaft by hand. Count the number of driveshaft revolutions required for one revolution of the tire.
If the driveshaft turns approximately 3-1/2 times, you have a 3.54 ratio, etc. It is helpful to use a grease pencil or chalk to make a reference point on both the tire and driveshaft while performing this test.