RE: Sound? What sound?
31's will be a tight fit with stock suspension and flares. My friend runs the same setup on his 4 banger YJ. It rubs a little on the flares but it has already worn them clear where it used to rub. I agree with nakedjeeper, stick with the 30's save for some gears and then get some big tires. But the 31's will work with the stock YJ.