Calculating Ring & Pinion Gear ratio
The easiest way to determine your ring & pinion gear ratio (sometimes called axle ratio) is to check the tag that's bolted to the front differential cover. On the tag you should see some numbering such as 3.07, 3.73 or 4.11. Any of these numbers are common for a Jeep stock axle ratio. If you want to double check (perhaps a previous owner regeared, wrong factory tag, etc), here's what to do:
Jack up the rear axle and support it with jack stands. Put the transmission in neutral and then rotate the rear drive shaft by hand. While turning, count the number of drive shaft revolutions required for one revolution of the tire. If the drive shaft turns approximately 3-3/4 times, you have a 3.73 ratio, etc. It may help to use a piece of chalk mark a reference point on both the tire and drive shaft. For increased accuracy it is recommended to rotate the wheels two times and divide the result by two. You may have different gearing front to rear (but the difference is typically very slight) so be sure to check the other axle too.
| Number of Turns | Approximate Gear Ratio |
|---|---|
| 2 - 3/4 | 2.72:1 or 2.77:1 |
| 3 - 0 | 3.07:1 |
| 3 - 1/2 | 3.54:1 |
| 3 - 3/4 | 3.73:1 |
| 4 - 0 | 4.10:1 |
| 4 - 1/2 | 4.56:1 |
| 4 - 3/4 | 4.88:1 |
Page created on 9/17/2003
Last updated on 4/18/2004