Most late model Sport and Sahara JKs come from the factory equipped with 3.21 axle gears rather than the optional 3.73 gears. The 3.21 gears with the new Pentastar V6 engine are fine around town but are marginal on hills, towing and off road. Most importantly, the 3.21 gears don't work well with oversize tires larger than 32".  3.73 gears are standard equipment on automatic Rubicons and raise the engine speed for more power. At 70 mph the engine will turn approximately 300 rpm faster than with 3.21 gears. Unlike numerically higher gear ratios used for rock crawling and heavy duty off roading, your JK will still be a great daily driver and gas mileage shouldn't change significantly

I'm selling the major components needed to upgrade from 3.21 to 3.73 gears as follows:

Lightly used, genuine Dana 30 front 3.73 ring, pinion and ring bolts,

Lightly used, genuine Dana 44 rear 3.73 ring, pinion and ring bolts, and

Lightly used 3.73+ carrier for Dana 30 front axle complete with spider gears and bearings (needed because the 3.73 front ring gear requires a larger carrier than the 3.21 front ring gear)