So picture this: you just got your new lift kit, bigger tires, and custom wheels installed on your Jeep Wrangler or Gladiator. You jump in, crank the engine over, and get ready to rip out to the local offroad park or ice cream shack. When you pull out of your driveway, hit the gas, it feels like you’re back in your 1988 Chevy Beretta that you drove to high school. All the power your Jeep once had is gone. It feels like you’re mired in the mud on pavement. What happened? How could you lose so much performance with only a simple lift kit, wheels, and tires? The answer is buried deep in your axles.

One of the most overlooked and misunderstood items required when modifying your Jeep Wrangler or Gladiator (or any offroad vehicle) is proper gearing. Your differential gears transfer power from your engine and transmission to your tires on the ground. This power transfer occurs between a ring and pinion gear set. Jeep Wranglers and Gladiators are geared from the factory to perform best in certain driving conditions. Jeep’s main concerns are fuel economy and performance on the street. When you go modify your Jeep with larger tires, add heavy steel bumpers and offroad equipment these stock gears become inadequate.

A ring and pinion works like a lever and a weight. When your Jeep is stock, the lever can be short because you have small tires and no extra weight. You can use that lever to effectively “pick up” what you are trying to lift. As you modify your Jeep, the weight on the end of the lever gets “heavier.” If you use that short lever to pick up the heavy weight, you work harder. Now imagine lengthening the lever. In principle, this is the same as adding a deeper or higher numerical gear ratio to your Jeep. The longer lever makes it easier to move the weight. With new gears, your Jeep will accelerate quicker and put more power to the tires. This is why choosing the proper gear ratio for your Jeep Wrangler or Gladiator is important.

At 4X Store, we are often asked, “What gear ratio do I need for my vehicle?” There is not a one size fits all answer. Gear choice depends on driving habits, vehicle weight, where you are wheeling, and your ultimate end goal. A new Jeep Gladiator JT with 37 inch tires you take trail riding will need a different gear ratio from the hardcore rock crawling rig on 42’s. While every custom application varies, the charts below represent typical ratio choices and their best matched tire sizes.

Gear ratio recommendations for Jeep Wrangler JK, JKU

With any tires 35 inches and larger on a JK/JKU, it’s time to consider a gear change. A new gear ratio will help give you as much performance as you can get out of your motor. While it is possible to undergear a vehicle, very rarely is it possible to overgear it. The more mechanical advantage you can give your Jeep, the easier it will work and the less trouble you will have getting rolling. The 3.8 liter engine in early JK/JKU Wrangler’s (2007-2011) benefits most from a gear change due to its lower power output. Check out this Jeep Wrangler JK & JKU ratio chart to help pick your correct gear size.

Gear ratio recommendations for Jeep Wrangler JL, JLU, & Gladiator JT

New Wrangler JL, JLU and Gladiator JT handle larger tires more easily, thanks to new engines and the introduction of an 8 speed automatic transmission. The new Jeeps also have more factory gearing options. JL, JLU & JT Jeep’s higher performance mechanicals mean larger tire diameters do not affect driveability as noticeably in comparison to the older JK & JKU Wranglers. However, a gear change is still recommended for the newer Jeeps with tire sizes above 35” and a factory gear ratio of 3:43 or 3:73. Check out this Jeep Wrangler JL, JLU and Gladiator JT chart to help pick your correct gear size.

Other Considerations

Gears are not the only component to upgrade in your Jeep’s axles when moving to larger tires. Lockers, axle shafts, differential covers and routine maintenance should all be considered while regearing, because it can be convenient and cost effective to replace these parts while your axles are disassembled.

If you are considering a tire size of 37 inches and up for your Wrangler or Gladiator and your Jeep will be tackling some tougher trails, you definitely need to start thinking about other chro-moly axle shaft upgrades and possibly complete custom axles as part of your regear. If you plan on playing in rocky terrain, this is the time to add a set of heavy duty differential covers to protect your new gears. Differential covers are cheap insurance to protect the expensive internal parts.

Axle upgrades are a big investment. The important factors to consider are your vehicles intended use, performance and reliability. For any questions or advice needed on gearing your Jeep, give us a call or find us on Facebook. See you on the trails!

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Find Your: Axle Shafts