Gear Howl and Whine
WARNING: This page is about a different car, the 2004 Ford RV Cutaway, 2004 Ford Econoline, 2004 Ford E450 Super Duty, and 2004 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
Howling or whining of the ring gear and pinion is due to an incorrect gear pattern, gear damage or incorrect bearing preload.