Those amplifiers in the late 80's to mid 90's trucks go bad and will make that noise. They are pricey if you can even find a good one. The best way to fix it is put in an aftermarket radio - unfortunately.
2003 Chevrolet Tahoe 4X4 5.3
2002 Chevrolet 2500HD 4X4 8.1 - BlackBear Tuned