Chevy truck makes grinding noise when it starts?

I have a 2000 chevy 3500 and every time i go to start it up it makes a horrible grinding noise. Once the engine is started and idling, it stops. Whats wrong, is the starter or something?|||starter bendix is going... thhe grind is the gaer meshing with the flywheel and not releasing... replace the starter|||sounds like the starter gear and ring gear are too far apart. A new starter motor will not fix this. The tranny ring gear is too warn. I quick fix this by filling away the starter mating surface away to bring the gears closer together. You can bring this back into spec with a serious parralel grinding off the starter housing mating flange. Hang on to that starter for future rebuilds.|||might be the starter... is it like the same kind of noise you'd get if you started up a car and cranked it again? cause thats a pretty god awful noise lol. I'd get it checked out, maybe the starter is on its way out.