1998 Chevy Astro knocking

On the way home a month or two ago, my astro van developed a real bad knock. It started out for a couple of miles when you pushed the accelerator and let go, you heard some tapping. That eventually got louder then all the sudden a terrible knock. I can't remember if it had loss of power or not. It's been sitting in the driveway for a couple of months b/c I just don't know what to do with it. I took off the belt to isolate and it still does it. It will start up perfect and idle fine, just with a very loud knock and a little squealing, all without the belt on. No engine light of course but where do you think I should start to look? I may just sell it for parts but I need to know what I'm up against. Thank you, Justin.