When & Why You Should Regear Your Wrangler

One of the most common modifications done to Wranglers is installing a lift kit and a larger set of tires. Something many people forget about when they install a larger set of tires is the drivetrain was geared to provide a balance between torque and top speed. When it comes to gear ratios the higher the number the more times the driving member needs to turn. For example, the first gear on an AX-15 transmission has a gear ratio of 3.83:1 and fifth gear has a gear ratio of 0.79:1.

Gears with lower numbers are referred to as taller and higher numbers are referred to as shorter. Taller gearing provides a higher top speed and better fuel economy while shorter gearing provides more low end torque and better acceleration. Taller gearing is better for daily driving especially if you are planning on doing a lot of highway driving or are simply going to run small tires. Shorter gearing is needed for large tires and also aids in rock crawling by increasing low end torque.

The gearing of your axles is set by the number of teeth on the ring and pinion gears. This determines how many times your driveshaft will have to rotate to spin the wheels once. A 4.10:1 gear ratio, for example, would mean that your driveshaft would have to spin 4.10 times to spin the wheels once.

The stock gear ratio tends to vary depending on the year and package your Jeep has. Some of the possible ratios include 3.07, 3.55, 3.73, and 4.10. Wranglers that are equipped with the Rubicon package typically come with the 4.10 gear set in their Dana 44 axles. The chart below shows the relationship between gear ratios and tire size. The numbers across the top are gear ratios, the numbers down the left side are tire sizes in inches, and the 4 digit numbers in the white boxes show RPM.

If you do a lot of highway driving on small to mid sized tires, it may be practical to regear to a taller setup to increase your top speed and fuel economy. If you are planning on doing a lot of off-roading or are only upgrading to a larger set of tires, you should probably install shorter gears.

When larger tires are installed, you have several things working against you: the diameter of the tire, rotational mass, rolling resistance, and the added weight of the tires. The diameter of your tires directly affects how hard your drivetrain has to work in order to move the vehicle, what you need to keep in mind is the axle is going to be turning your wheels. The axle shafts are just over an inch in diameter, and they have to turn whatever tires are on your Wrangler. This means that with a 30 inch tire you need to apply 30 times more force to the axle in order to turn the wheel. By regearing to a shorter gear, you will increase the amount of force that is being sent to the axle, this allows your Jeep to move the tires with less of a strain on the engine.

Replacing your Jeep's ring and pinion gears is more than simply purchasing a ring and pinion set. There are a number of bearings, seals, bolts, and the differential cover gaskets to worry about. If you're replacing the gears in both front and rear differentials, your overall cost will be understandably more. An entire gear overhaul kit will run you anywhere from $600-$1,200.

Certain differentials can only accommodate certain size ring gears. Generally, the higher numerically you go in gears, the bigger the ring gear. Should you need to upgrade the differential's carrier, this is the time to decide if you want to upgrade to lockers. No reason to do the work twice should you decide on lockers later. A new differential carrier will run about $700-$1,000.

Labor will always vary by region and shop, but you expect a ring and pinion gear installed to be approximately $500-$700 per axle. The being said, a complete regear job is several thousand dollars, done properly. 

Unless you're familiar with wrenching on your Wrangler (more than oil changes and filter swaps), we highly recommend bringing your Jeep to a professional to have ring and pinion gears installed. What follows is a simplified version of how to install gears in your Jeep. For a more detailed look, see our related installation guides.

• Drain the differential's gear oil
• Remove the axle shafts
• If you're not replacing the main caps, mark them so you know which side they came from
• Clean all new parts and remove any metal shaving within the carrier
• Coat all new bearings and seals with fresh gear oil
• Install the ring gear on the carrier, checking for proper shimming and backlash
• Install the pinion gear and press on the carrier bearing, checking for proper bearing preloads
• Reinstall the entire assembly into the differential housing