Ford 2003 Mustang Workshop Manual page 346

If the runout does not exceed the specification, use the new differential bearings for
assembly.
If the runout exceeds the specification, install a new differential case. For additional
information, refer to
20. Remove the differential assembly from the differential housing.
Installation
All axles
1. Position the ring gear and the differential case. Align the bolt holes by starting two bolts through
the holes in the differential case and the ring gear. Press the ring gear on the differential case.
2. Install the bolts.
Apply Stud and Bearing Mount EOAZ-19554-BA or equivalent meeting Ford specification
WSK-M2G349-A1 to the bolt threads.
3. With the pinion depth set and the pinion installed, place the differential assembly in the
differential housing.
Differential Case and Ring Gear in this section.