Quote Originally Posted by cmdr jim View Post
07JeepXK has helped a friend swap gears in there 3.07 WK. You can go 3.55 or 3.73, Yes you will have to buy the front gears from Jeep or find a used front differential or gears. The rear is a Chrysler 8.25 differential with 29 tooth spline. Those are available aftermarket. If you're going into the rear end put in some type of locker while it's open. Lastly, according to 07JeepXK, a HyperTech Speedo Calibrator or MAX Energy Programmer is needed to program in the new gear ratio.

Note: I will have available in a couple weeks a used set of 3.55 front ring and pinion gears with about 35,000 miles on them and a new set of Mopar 3.55 rear ring and pinion gears for sale, if anyone is interested, I can give you a good price on these. The Front new is $855 from a dealer and about $600 shipped from an online Mopar parts store. The rear would go for $462 or $350 shipped. I could do $300 for the set, that includes shipping.
Like stated by cmdr jim, your best bet is to get an entire front differential from a junk yard that already has 3.73 gears installed. That makes the swap so much easier and costs a lot less. All you have to do is drop the front diff and swap in the new one. As for the rear my buddy Jay purchased 3.73 motive gear ring and pinion for a chrysler 8.25 rear end. After everything is installed, purchase the Hypertech Speedometer Calibrator and change the gear ratio from 3.07 to 3.73's and enjoy! The Hypertech Speedometer Calibrator is upgradable to the max pro so you can tune your 3.7 liter at the same time. Jays 3.7 Liter WK has been rolling around with 3.73s with ablsolutely no issues what so ever and his gas mileage has even increased. He has a 4 inch BDS lift with 33x12.5R18 Toyo Open Country MT's.