The first thing that comes to mind is your brake pads. Is it worse when you apply the brakes? It might even pull one way or the other when braking?? If not, can you tell if its coming from front? Rear? The more info the better, but metal on metal is not good and needs to be checked out asap
I just re read your post.. Screeching vs scraping is way different. Screeching could be the wear indicator on your pads. Possibly time for some new ones before they wear out and eat into your rotors
2005 Tj, BDS long arm, d60hp front, 10.25 rear, 513s and lockers, f&r winches, 39.5" Iroks