Testing Procedure

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

Wipe clean the differential case, the ring gear and the axle housing of lubricant. Carefully clean each tooth of the ring gear.
Use a medium stiff brush in order to sparingly apply gear marking compound, GM P/N 1052351 (Canadian P/N 10953497) or equivalent, to all of the ring gear teeth.

Fig 1: Applying Gear Marking Compound
Courtesy of GENERAL MOTORS CORP.

Important: Avoid turning the ring gear excessively.
Turn the drive pinion so that the ring gear rotates 3 full revolutions.
Turn the drive pinion in the opposite direction so that the ring gear rotates 3 full revolutions in the opposite direction.
Observe the pattern on the ring gear teeth. Compare the pattern with the following illustrations.