Ford 2003 Mustang Workshop Manual page 113

Tooth contact pattern shown on the drive side of the gear teeth.
The high contact pattern indicates that the drive pinion is not installed deep enough into the
carrier.
The differential ring gear backlash is correct, a thinner drive pinion shim is needed. A decrease
will move the drive pinion toward the differential ring gear.
9. A high, thin contact pattern that is worn toward the toe.
Tooth contact pattern shown on the drive side of the gear teeth.
The drive pinion depth is correct. Increase the differential ring gear backlash.
10. A contact pattern that is worn in the center of the differential ring gear tooth toward the heel.
Tooth contact pattern shown on the drive side of the gear teeth.
The low contact pattern indicates that the drive pinion is installed too deep into the carrier.
The differential ring gear backlash is correct. A thicker drive pinion shim is needed.
11. A contact pattern that is worn at the top of the differential ring gear tooth toward the heel.