727 internal scraping noise

First thing I would check is the dust shield. A slight rub can make a horrific sound. I agree, starting in gear shouldnt have hurt anything. Hopefully your sprag is ok. I had a sprag let loose while driving and it didnt hurt the case at all. Not sure how, the rollers and springs were mangled to hell. I dont build them without an upgraded sprag anymore.
Do you hear the noise when its in park or only when your moving?