I am hearing noise from my rear differential on 2005 Mercury Mariner

This 2005 4WD 6 cyl. Mercury Mariner has 130,000 miles. I am hearing noise ( grinding, pulsating ) from differential.Fluid levels, shifting functions are all OK. Metal shavings in pan are present. Is it ready to fail?

Asked by for the 2005 Mercury Mariner
Sounds like the differential bearings are worn out, grinding up and failure is imminent. It's cheaper to address this before the gears are damaged by the metal chips in the oil.
I have a 2008 Mariner.The differential needs replaced.What could the cost be.