One problem related to power train driveline has been reported for the 2004 Jeep Wrangler. The most recently reported issues are listed below.
While moving rocks in my yard, I put the transfer case in low and locked the axles, both front and rear. The front driver side u-joint exploded, damaging the inner and outer axles. The vehicle was undrivable. I do failure assessment for my work and have determined incorrect heat treating of the critical drive train components to be suspect. This is suppose to be a heavy duty vehicle. Moving rocks is hardly heavy duty. There are also a lot of "replacement" axles available on the aftermarket that state they are "more" heavy duty than stock. A neighbor down the street experienced the same failure prior to me. My vehicle missed the warranty by 2,700 miles but is 2 years under. Repairs are expected to be $1,000 plus labor.