One problem related to loud engine noise has been reported for the 2003 Chevrolet Silverado. The most recently reported issues are listed below.
First time:main computer failed. Second time:stalling, running rough, boggs down and makes loud noise,mis-fire in #5 & #6 cilander. A/c not working. Not fixed. Third time: everything same as second time and engine light now coming on. Not fixed. Fourth time:all lights on dash come on and all messages appearing on message board. Not fixed. After computer changed truck preformed unsatisfactory and is still unsatisfactory. All having to do with computer. Told it is a random problem that is hard to detect and may not ever be fixed.