I just had this exact same issue on a new engine I put together. Only a hundred miles on it before it started the loud whine. Took the belt off and changed power steering pump and it was still there.
So off comes the the front cover. Found this...
The idler shaft on the oil pump completely came loose from the casting.
Moral of the story, DO NOT buy aftermarket oil pumps. I'll only use original cummins oil pumps now.