Checking Tooth Contact Pattern and Condition of the Ring and Pinion

There are two basic types of conditions that will produce ring and pinion noise. The first type is a howl or chuckle produced by broken, cracked, chipped, scored or forcibly damaged gear teeth and is usually quite audible over the entire speed range. The second type of ring and pinion noise pertains to the mesh pattern of the gear pattern. This gear noise can be recognized as it produces a cycling pitch or whine. Ring and pinion noise tends to peak in a narrow speed range or ranges, and will tend to remain constant in pitch.

1. Raise and support the vehicle.
2. Drain the axle lubricant.
3. Remove the carrier assembly or the axle housing cover depending on the axle type.
4. Inspect the gear set for scoring or damage.
   Fig 1: Identifying Crown Wheel

   Courtesy of FORD MOTOR CO.
   Fig 2: Identifying Damaged Gear Teeth

   Courtesy of FORD MOTOR CO.
5. In the following steps, the movement of the contact pattern along the length is indicated as toward the "heel" or "toe" of the differential ring gear.
   Fig 3: Locating Differential Ring Gear Heel And Toe

   Courtesy of FORD MOTOR CO.
6. Apply a marking compound to a third of the gear teeth on the differential ring gear. Rotate the differential ring gear several complete turns in both directions until a good, clear tooth pattern is obtained. Inspect the contact patterns on the ring gear teeth.
7. A good contact pattern should be centered on the tooth. It can also be slightly toward the toe. There should always be some clearance between the contact pattern and the top of the tooth.
   • Tooth contact pattern shown on the drive side of the gear teeth.
   Fig 4: Identifying Tooth Contact Drive Side Gear Teeth

   Courtesy of FORD MOTOR CO.
8. A high, thick contact pattern that is worn more toward the toe.
   • 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.
   Fig 5: Identifying High Thick Contact Tooth

   Courtesy of FORD MOTOR CO.
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.
   Fig 6: Identifying Tooth Contact Pattern Shown Drive Side Gear Teeth

   Courtesy of FORD MOTOR CO.
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.
    Fig 7: Identifying Low Contact Drive Pinion

    Courtesy of FORD MOTOR CO.
11. A contact pattern that is worn at the top of the differential ring gear tooth toward the heel.
    • Tooth contact pattern shown on the drive side of the gear teeth.
    • The pinion gear depth is correct. Decrease the differential ring gear backlash.
    Fig 8: Identifying Tooth Contact Drive Side Gear Teeth

    Courtesy of FORD MOTOR CO.