The jeepfan.com 2004 TJ Unlimited was going to get some bigger tires which will impact drive-ability in a few ways, most notably here being the effect of larger tires on gearing. Larger tires will effectively increase the overall gear ratio since the tires cover more distance per revolution. This could make a Jeep with a 3.73 gear ratio act like a Jeep with 3.21. This kills fuel economy and overall performance.
To compensate for the change lowering the gear ratio will restore the Jeep to its original overall ratio. So how do we figure this out?
The jeepfan.com TJ was originally equipped with 3.73 gears and an automatic transmission with an overdrive. 2004 was the first year for the 4 speed auto and it really makes a difference with selecting ratios. The overdrive allows for lower ratios without sacrificing highway driving.
Using a gear calculator and knowing the new tire size the best ratio was 4.56. This actually increases the highway RPM slightly giving the Jeep a better power feel.
G2 Ring and Pinion Set
We chose gears from G2, Quadratec sells a complete front and rear set that includes a full installation kit. We were combining the gear change with the ARB Air Locker installation to make this a once and done project.
Installation
Replacing a set of ring and pinions is often something that most of us Jeepers can’t do at home since installation requires specialized tools. We took both the front and rear axles to OK Auto to have them all setup.
We removed the axles from the TJ, but it’s not always necessary to do this. Most of the time gear changes can happen with the axles still in the Jeep.
With the gears properly setup within the axle and on the new ARB Lockers it was time for installation back in to the Jeep. This whole project included the ARB Air Lockers and a 3″ Teraflex Lift. Additional add-ons were ARB Heavy Duty differential covers and an ARB Air Compressor.
