Some 2007-11 Ford Fusions, Mercury Milans and Lincoln MKZs with AWD systems may produce a howling noise and/or vibration from the driveline in colder temperatures.
According to Ford, the trouble is most obvious while driving at highway speeds and likely is due to premature wear in the front and/or rear bearings of the rear driveshaft assembly.
To make the diagnosis, place the vehicle in neutral, then raise it on a lift.
Next, place index marks at both driveshaft flanges and disconnect the rear driveshaft from the PTU and differential (leave the driveshaft attached to the vehicle).
Now rotate the driveshaft by hand and feel for roughness in the front and rear bearings. If no roughness is felt, this information doesn't apply; continue searching for the cause of the noise or vibration.
If you do feel roughness, replace the rear driveshaft with an updated, improved unit, part No. AE5Z-4R602-A.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected].