Ring and Pinion Contact Pattern Checking Procedure

1. Apply a light coating of gear marking compound to all ring gear teeth not making contact with the pinion gear.
2. Insert a standard drift punch between the ring gear and the differential carrier to bind the ring gear and simulate a drag.
3. Using a wrench, slowly and evenly turn the pinion gear until the ring gear has made one complete revolution. Because of the drag simulated on the ring gear, this will produce a contact pattern on the drive side of the ring gear (pinion gear driving ring gear).

Important: In order to ensure an accurate gear contact pattern, make sure the ring gear turns one revolution only.

4. Turn the pinion gear in the opposite direction with drag simulated on the ring gear and a contact pattern on the coast side of the ring gear (ring gear driving pinion gear).








The drive side of the ring gear tooth is convex and the coast side of the ring gear tooth is concave. The contact pattern area should be even around the ring gear. Uneven contact around the ring gear indicates excessive ring gear runout. The drive pattern should be centrally located between the top and bottom of the ring gear tooth. Under an increased load, the pattern spreads out and tends to move toward the heel of the tooth. To compensate for this, the contact pattern can be somewhat closer to the toe. Under heavy loading conditions, uphill or rapid acceleration, the pattern may extend almost the full distance from toe to heel. Use the "Gear Contact Patterns" chart to determine if a correct contact pattern exists. If excessive contact pattern error is present with proper backlash specification. check pinion for proper selective shim.