Gear Howl and Whine
WARNING: This page is about a different car, the 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, 2004 Ford Excursion, and 2004 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Howling or whining of the differential ring gear and pinion is due to an incorrect gear pattern, gear damage or incorrect bearing preload.