Later model 4.0s seem to have sporadic lifter quality problems. Mine went south at about 50,000K; took the cam with it. Do some searching, you'll see the threads.
Mine didn't make noise every time I started the engine cold, it only "clattered" sporadically. Not sure whether rods would quiet when the engine warmed up unless the problem is piston slap, which I think is rare on the 4.0s. Generally, the lifters quiet down when pumped up with oil.
04 Unlimited, White, Soft Top, 4spd auto
2002 Camp Jeep Tire Cover my Brother gave me
Failed Lifters Club Member