Originally Posted by T.Dot_E30
Actually it's starting to sound more like the AC compressor bearing.
See if you can put your hand on the compressor while the engine is running. (without touching the belt of course) If it feels like metal on metal 'grinding' then it's probably that. Another way is to disconnect the AC belt since it's separate from other accessories.
Happened to my dad's old RAM last year during summer. Man did it sound bad. I would check this as well. I know on the Mazdaspeed3, when the defrost is activated, the a/c belt spins once every few minutes which helps keep it from seizing over winter.