One way to determine your gear ratio is to check the tag attached to the front 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 would indicate the stock axle ratio. To verify this 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. Your gears may have been swapped out if it's a used vehicle so verification is just an extra step to be sure of the ratio.
If the driveshaft turns approximately 3-1/2 times, you have a 3.54 ratio, etc. It's helpful to use a grease pencil or chalk to make a reference point on both the tire and driveshaft.
Number of Turns Approx. Gear Ratio
3 3.05 : 1
3 1/2 3.54 : 1
3 3/4 3.73 : 1
4 4.10 : 1
4 1/2 4.55 : 1
