73delta88 has it right on the Delco batteries are well known for acid leakage atthe pos bat terminal (sidepost) the acid will corrode the connection/bolt and will a majority of times soak down the cable (capilary action) a ways and corrode the copper wire from the inside out.
i have seen some cables where they are corroded 3 ft down the length and reduced to nothing but greenish powder!! if this is the case you will notice that the battery cable has swelled in size (most are 4 gauge cables but will look like giant 2 ga in the heavy corrosion area's).
a good majority though just have the terminal/bolt coated with corrosion which will sometimes needs to be chipped off and cleaned up/sanded.
there is always the poss of a bad starter but i havent replaced many 96 and later GM starters as i have found the batt/cables to be the culprit in over 80% of my repairs.
also some advice---if you have corrosion on the cables ends but not inside the cable (sometimes it helps to cut the red terminal boot off with a razor blade) get a box of baking soda and wet down the whole batt area (remove batt and do under it also) and spread it around libberally to nutralize any acid that may be eating away your cars sheetmetal and soak the end of the cable in a big cup of Bakingsoda/water to nutralize the acid inside it (will keep the cable ok longer but rec replacing if cable really corroded)-make sure you use the whole box! i have had vehicles take scrubbing with two boxes worth several times before the Bsoda stopped foaming/ and finished nutralizing the acid (had to git a new batt tray on that car as it was completely eaten through!)
welcome to the site and hope this helps ya some more.
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Psychotic Gearhead/Redneck/Mekanik
94 Olds 442 Twin engine's! 6.9L/425 cu inches and 12 cylinders!
13.81 @ over 98 MPH! consistent 1.9s 60'!