Ring and pinion gears are supplied as matched sets. The identifying numbers (3) for the ring and pinion gear are etched into the each gear. A plus (+) number, minus (–) number or zero (0) is etched into the face of the pinion gear (2). This number is the amount (in thousandths of an inch) the depth varies from the standard depth setting of a pinion etched with a (0). The standard depth provides the best gear tooth contact pattern. Refer to Backlash and Contact Pattern in this section for additional information.If a new gear set is being installed, note the depth variance etched into both the original and replacement pinion. Add or subtract this number from the thickness of the original depth shim/oil slinger to compensate for the difference in the depth variances. Refer to the Depth Variance chart.Note where Old and New Pinion Marking columns intersect. Intersecting figure represents plus or minus the amount needed.Note the etched number on the face of the pinion gear head (–1, –2, 0, +1, +2, etc.). The numbers represent thousands of an inch deviation from the standard. If the number is negative, add that value to the required thickness of the depth shims. If the number is positive, subtract that value from the thickness of the depth shim. If the number is 0 no change is necessary.Original Pinion Gear Depth VarianceReplacement Pinion Gear Depth Variance−4−3−2−10+1+2+3+4+4+0.008+0.007+0.006+0.005+0.004+0.003+0.002+0.0010+3+0.007+0.006+0.005+0.004+0.003+0.002+0.0010−0.001+2+0.006+0.005+0.004+0.003+0.002+0.0010−0.001−0.002+1+0.005+0.004+0.003+0.002+0.0010−0.001−0.002−0.0030+0.004+0.003+0.002+0.0010−0.001−0.002−0.003−0.004−1+0.003+0.002+0.0010−0.001−0.002−0.003−0.004−0.005−2+0.002+0.0010−0.001−0.002−0.003−0.004−0.005−0.006−3+0.0010−0.001−0.002−0.003−0.004−0.005−0.006−0.007−40−0.001−0.002−0.003−0.004−0.005−0.006−0.007−0.008

Measurements are taken with pinion bearing cups and pinion bearings installed in the housing. Take measurements with Pinion Gauge Set 6730 (2,3,4,5,6,7,8) and Dial Indicator C-3339A (1).

Assemble Pinion Height Block 6739 (2), Pinion Block 9990 (1) and rear pinion bearing onto Screw 6741 . Insert assembled height gauge components, rear bearing and screw into the housing through pinion bearing cups.Install front pinion bearing and Cone-nut 6740. Tighten nut until a Torque To Rotate the screw is 2.25 N·m (20 in. lbs.).

Place Arbor Disc 8541 (1) on Arbor D-115-3 (2) in position in the housing side bearing cradles .Arbor Discs 8541 has different step diameters to fit other axles. Choose proper step for axle being serviced.

Install differential bearing caps (1) on arbor discs (2) and install bearing cap bolts. Tighten bearing cap bolts to 108 N·m (80 ft. lbs.).

Assemble Scooter Block D-115-2A (1) and Dial Indicator C-3339A (2) secure set screw.Position Scooter Block/Dial Indicator flush on the pinion height block. Hold scooter block and zero the dial indicator.Slowly slide the scooter block (1) across the pinion height block over to the arbor. Move the scooter block till dial indicator (2) crests the arbor, then record the highest reading.Select a shim equal to the dial indicator reading plus or minus the pinion depth variance number etched in the face of the pinion. Example: If the depth variance is –2, add 0.002 in. to the dial indicator reading. If the depth variance is +2, subtract 0.002 in. from the dial indicator reading.The total is the shim thickness needed for the pinion depth variance.

Before performing differential bearing preload and ring gear backlash measurements, pinion gear depth must be established and the pinion gear ready for installation. Establishing pinion gear depth is essential to gear backlash and tooth contact patterns.Differential bearing preload and gear backlash is accomplish with selective shims (2,4) positioned behind the differential side bearing cups. Shim thickness is determined using Dummy Bearings 9992 in place of the differential side bearings and a Dial Indicator C-3339A. SHIM FORMULA: Differential End Play + Preload Specification = Total Shims. Total Shims – Ring Gear Side Shim – Backlash Specification = Pinon Gear Side Shim.

Remove differential side bearings from differential case.Remove factory installed shims from differential case.Install ring gear on differential case and tighten bolts to specification.Install dummy side bearings 9992 on differential case.Install differential case (3) in the housing (2).Install bearing caps (1) in original location and snug the bolts.

Seat differential (3) dummy bearings to pinion side (2) of the housing with a dead-blow hammer (1).

Seat differential (3) dummy bearings to ring gear side (1) of the housing with a dead-blow hammer (2).

Thread Pin C-3288-B (3) into cover bolt hole below ring gear.Attach the Dial Indicator C-3339A (4) to the pin. Position the dial indicator plunger on a flat surface between the ring gear bolt heads.

Push and hold differential case (1) to pinion gear side of the housing and zero dial indicator (2).

Push and hold differential case (2) to ring gear side of the housing. Record dial indicator (1) end-play reading. Add 0.25 mm (0.010 in) preload specification to end-play reading. This is the total shims needed to preload the differential bearings.Rotate dial indicator out of the way on the pilot stud.Remove differential case and dummy bearings from the housing.Install pinion gear in the housing and establish pinion torque to rotating (PTTR).

Install differential case and dummy bearings 9992 in the housing, install bearing caps and snug bolts.Seat ring gear side dummy bearing.Position dial indicator (2) plunger on a flat surface between the ring gear bolts.Push and hold differential case (1) against pinion gear and zero dial indicator (2).

Push and hold differential case (2) to ring gear side of the housing and record dial indicator (1) ring gear side reading.Subtract backlash specification 0.05 mm (0.002 in.) from ring gear side reading for ring gear backlash. The remainder is the shim needed for the ring gear side of the differential.Subtract ring gear side shim from the total preload shim. The is the shim needed on the pinion side of the differential.Rotate dial indicator out of the way on pilot stud.Remove differential case and dummy bearings from the housing.Install side bearings on differential case.

Install Spreader W-129-B (1) with hold downs (2) from Adapter Set 6987B on the housing and spread open enough to receive differential case.Never spread housing over 0.50 mm (0.020 in). Failure to follow these instructions will damage the housing.

Install differential case (2) into the housing with bearing cups (3) and shims.

Install bearing caps and tighten bolts finger tight. Remove spreader from the housing.Install bearing cap (1) and tighten bolts to 108 N·m (80 ft. lbs.).Rotate the differential case several times to seat the side bearings.

Position dial indicator plunger against a ring gear tooth.Push and hold ring gear upward while not allowing the pinion gear to rotate.Zero dial indicator (1) face to pointer.Push and hold ring gear downward while not allowing the pinion gear to rotate. Dial indicator reading should be between 0.12 mm - 0.20 mm (0.005 in - 0.008 in). If backlash is not within specifications transfer the necessary amount of shim thickness from one side of the housing to the other.

Verify differential case and ring gear runout by measuring ring to pinion gear backlash at eight locations around the ring gear. Readings should not vary more than 0.05 mm (0.002 in). If readings vary more than specified, the ring gear or the differential case is defective.After the proper backlash is achieved, perform Gear Contact Pattern Analysis procedure.

The ring gear and pinion teeth contact patterns will show if the pinion depth is correct in the housing. It will also show if the ring gear backlash has been adjusted correctly. The backlash can be adjusted within specifications to achieve desired tooth contact patterns.The TOP LAND (1) of the gear tooth is the top surface of the tooth. The PROFILE (2) of the gear tooth is the depth of the tooth. The TOE (3) of the gear is the portion of the tooth surface at the end towards the center. The HEEL (4) of the gear is the portion of the tooth at the outer-end. The ROOT (5) of the gear tooth is the lowest portion of the tooth .If the PROFILE across the tooth is the same it is a 3 Axis cut gear. If the PROFILE across the tooth is tapered it is a 2Axis cut gear. Apply a thin coat of hydrated ferric oxide or equivalent to the drive and coast side of the ring gear teeth.Wrap, twist and hold a shop towel around the pinion yoke to increase the turning resistance of the pinion. This will provide a more distinct contact pattern.With a boxed end wrench on the ring gear bolt, rotate the differential case one complete revolution in both directions while a load is being applied from shop towel.The areas on the ring gear teeth with the greatest degree of contact against the pinion teeth will squeegee the compound to the areas with the least amount of contact. Note and compare patterns on the ring gear teeth to Gear Tooth Contact Patterns chart adjust pinion depth and gear backlash as necessary.THREE AXIS CUT GEAR

TWO AXIS CUT GEAR

The final check on the differential assembly before installing the axle shafts is torque to rotate pinion and differential combined. This will verify the correct differential bearing preload.Total Torque To Rotate (TTTR) is: Pinion Torque To Rotate plus 0.79 - 1.24 N·m (7 - 11 in lbs).If TTTR is high, decrease the shim thickness equally on both sides of the differential and check TTTR again. If TTTR is low, increase the shims thickness equally on both sides of the differential and check TTTR again.