I am experiencing a loud noise coming from front drivetrain,transfer case?

Could be the power steering pump is noisy from air bubbles in fluid. My 99 taurus does it when the system needs to be bleed of air. Does the P/S fluid leak out top of reservoir when you turn it off? Then air is in system and gets pressurized, then releases and "burps" when you shut it off. check procedure for bleeding power steering system.