After you’ve lifted your XJ Cherokee you’ll probably want to put some larger tires on it. If you’re upgrading to 31-inch tires you’ll probably be fine with the stock gear ratios in your axles. If you’re upgrading to 33 or 35-inch tires, however, you’re going to want to change the factory gear ratios. In this short guide, we’ll cover what gear ratios you’ll want for specific tire sizes.

Why Upgrade?

The stock 3.55:1 gear ratio you find in most automatic XJ Cherokee’s is perfect for the stock tire size or even a little bit larger. We’ve seen XJs on 37-inch tires run the stock gear ratios, but it was struggling to turn to those big tires. As you increase the size of the tires you effectively raise your gear ratio. Higher gear ratios are great for fuel mileage since your engine will be turning at a slower speed, but they’re not good for off-roading.

If you make your gear ratio lower, it multiplies engine torque. The more effective torque you have, the easier it will be to crawl up obstacles. The whole idea behind lowering your gear ratio as you increase tire size is to maintain the effective drive ratio of a stock XJ Cherokee. If your effective drive ratio isn’t near the stock ratio it can cause transmission issues amongst many other problems. If you’re building a crawler you’ll obviously want an even lower gear ratio for more torque.

Below is a handy chart that can be used as a guideline when decided your gear ratio. You can also use the equation of stock tire height times stock gear ratio all divided by your desired tire size.

Gear Ratio For 33-Inch Tires

When you upgrade to 33-inch tires you can run stock gearing, but we strongly don’t recommend it. A good gear for an AW4 automatic with 33-inch tires is a 4.10:1 or 4.56:1 gear ratio. Both of these will keep you around the stock drive ratio. Personally, we think the 4.56:1 gear ratio is better thanks to its improved acceleration and crawling abilities.

Coil spring swapped XJ on 33-inch tires

For an AX-15 manual, you’ll want around a 3.55:1 gear ratio. Fortunately, most automatic XJs have 3.55:1 gear ratios so upgrading should be pretty cheap if you opt for used axles.

Gear Ratio For 35-Inch Tires

For 35-inch tires, the stock gearing is really going to struggle. Unless you have a V8 swapped engine we strongly don’t recommend using the stock gearing. A good gear ratio for the AW4 automatic running 35-inch tires is 4.56:1 or 4.88:1 gear. Part of the reason we recommend 4.56:1 gears for the 33-inch tires is because they also work well with 35-inch tires. If your Jeep has the AX-15 automatic you’ll want around a 4.10:1 gear ratio.

At this tire size, you’ll also want to look into upgrading your rear axle to a Ford 8.8 or Dana 44. Make sure whatever gears you buy will work with the axles you’re buying.

Gear Ratio For 37-Inch Tires

At the 37-inch tire size, you’ll probably want to upgrade to full-size axles. You can make narrow width axles work, but you better get used to swapping axles shafts. If you’re running an AW4 automatic, a good gearing ratio for 37-inch tires is 4.88:1 or 5.13:1 gears.

If your Jeep is equipped with an AX-15 automatic you’ll probably want 4.56:1 gears. At this tire size, your Jeep won’t be very street friendly so an even lower gear ratio than what we recommend might be better for crawling.

Gear Ratio For 40-Inch Tires

At the 40-inch tire size, your XJ will basically be un-driveable on the street. Depending on what axles your Jeep has, your gear selection may be limited. The Jeep in the photo below is running 5.13 gears on 40” tires, but with the addition of an Eaton M62 supercharger.

If your Jeep is just a stock 4.0-liter you’ll want anything from a 5.29:1 to 6.17:1 gear ratio for the AW4 automatic. If your Jeep has an AX-15 you’ll probably want 4.88:1 or 5.13:1 gears to make crawling as easy as possible.

XJ Crawler on 40-inch stickies.

Summary

Forums are a great place to find out if people are happy with their current gear/tire combo. Below is a chart that can be used as a guideline for what combos are good. You also need to know what you’re doing with the Jeep and if it needs to be used on the street.

If it’s a daily driver we recommend keeping the drive ratio near stock. If it’s going to be used for crawling we recommend running a lower gear ratio.