Mine was a dog on 31's with 4:10 gearing, and stock 2.5L, so I switched to 30" tires and have a pro-comp 2" lift. The 2.4l has more horsepower from the factory as well. I would rather have my 2.5 l motor though, personally, no offense. You will have driveshaft vibrations that only a slip yoke eliminator kit can positively remove from what I have gathered, and it is more money than I can part with, like $700.00. I use the transmission skid plate lowering kit, and still have some vibrations. Mine is a daily driver though, and I live in a mountainous/hilly area. In places like Kansas, or flatlands, Jeeps may not have such a difficult time with 31's, and stock gearing.
Not to brag, but since I couldn't afford the re-gearing of both axles, I nickle and dimed a banks torque tube header, flowmaster muffler, rock -it intake, power-aid throttle body spacer, and a K&N filter which gave me noticeable power, but maybe not enough to run 31's without power problems. I have yet to try any larger size tires since I added the performance modifications though.