Some 2007-’11 Fusion, Milan and MKZ vehicles equipped with all-wheel-drive (AWD) systems and built on or before 8/13/2010 may exhibit a driveline vibration or a howl at highway speeds in cold temperatures.
1. Place the vehicle in neutral on a lift.
2. Index-mark both the driveshaft flanges at the power transfer unit (PTU) and rear differential unit (RDU).
3. Disconnect the rear driveshaft from the PTU and from the RDU assembly. Leave the driveshaft attached to the vehicle.
4. Rotate the driveshaft by hand, and check for any roughness feel to both the front and rear driveshaft bearings.
a. If no roughness is felt from either bearing, do not continue with this procedure and re-index the driveshaft.
b. If any roughness is felt from either bearing, replace the driveshaft assembly.
Courtesy of ALLDATA.