One problem related to engine clicking and tapping noises has been reported for the 2004 Chevrolet Silverado. The most recently reported issues are listed below.
Light ticking noise from engine from about 30,000 miles by 45,000 miles the noise is much more noticeable like lifters tapping. Failure was with one of the cam shaft lobes chipping off a substantial piece of metal ( brake failure as opposed to being wiped ). The repair has not yet been completed but will require new cam shaft, lifters, head bolts, gasket kit.