Ford 2003 Mustang Workshop Manual page 470

30. Install the differential case. Rotate the differential case to seat the differential bearings.
31. Using the special tool, measure the differential case flange runout.
If the runout does not exceed the specification, the cause of the original excessive runout
is the differential ring gear. Remove the differential case. Discard the differential ring gear
and the drive pinion gear. Proceed to Final disassembly in this procedure.
If the runout exceeds the specification, the differential ring gear is true and the concern is
due to either differential case/differential bearing damage. Remove the differential case.
Discard the differential bearings/differential case. Proceed to Final disassembly in this
procedure.
Remove the special tool.
Final disassembly
32. If not done previously, remove the bolts.