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. For additional information, refer to JACKING & LIFTING .
2. Drain the axle lubricant. Refer to REAR DRIVE AXLE/DIFFERENTIAL - FORD 7.5" RING GEAR for Ford 7.5 rear axles, REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8" RING GEAR for Ford 8.8 rear axles or FRONT DRIVE AXLE/DIFFERENTIAL - DANA 35 for front axles.
3. Remove the carrier assembly or the axle housing cover depending on the axle type. Refer to REAR DRIVE AXLE/DIFFERENTIAL - FORD 7.5" RING GEAR for Ford 7.5 rear axles, REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8" RING GEAR for Ford 8.8 rear axles or FRONT DRIVE AXLE/DIFFERENTIAL - DANA 35 for front axles.
4. Inspect the gear set for scoring or damage.
   Fig 1: Inspecting Gear Set For Scoring

   Courtesy of FORD MOTOR CO.
   Fig 2: Inspecting Gear Set For Damage

   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: Identifying Ring Gear Heel & 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 Good Contact Pattern

     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 Thick Contact Pattern - Worn More Toward Toe

     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 Thin Contact Pattern - Worn Toward Toe

     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 Center Of Differential Ring Gear Contact Pattern

      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 Top Of Differential Ring Gear Contact Pattern

      Courtesy of FORD MOTOR CO.