1998 Chevy Astro noises on diffrential

I was driving in expressway all of sudden heard, like the transmission, came off. Kept driving till I reached, an auto tire mechanic. He checked say. That the top from the oil cover was missing and lost all oil.I went and bough new iol. And a new cap. After, putting new oil and cap.I still hear a soun. It drives but with a sound. My husband checked under. And says it needs a newfront differential. We have searched the junk yards but no luck. Can you help me. Wew are stranded.