Rear driver side wheel grinding and metal gears inside rotor. on 2004 Chevrolet Suburban 1500

Grinding started from brake pad pieces falling from pad into inside dust shield moved into a loud grinding. I cut off the inside dust shield to see two small pieces of metal including one small gear like piece inside the rotor... scared to drive it somewhere, but have no idea where to start... I am a capable mechanic if I have the right part and diagnostic. thanks!

Asked by for the 2004 Chevrolet Suburban 1500
The toothed gear wheel sounds like it may be the ABS wheel speed tone ring, should see a electrical hall effect sensor in close proximity. Is the wheel bearing that bad that it is decintagrating ? Autozone have some popular workshop manuals for free on line once you register (for free) on their website There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate