Rear Axle-248RBI

PINION DEPTH-BEARING PRELOAD GEAR BACKLASH





Ring and pinion gears are supplied as matched sets. Identifying numbers (3) for the ring and pinion gears are etched into the face of 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.





Compensation for pinion depth variance is achieved with a select shim (1). The shims are located between the rear pinion bearing and pinion gear head.
If installing a new gear, note the depth variance number of the original and replacement pinion. Add or subtract this number from the original depth shim/oil slinger to compensate for the difference in the depth variances. 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.
Pinion Gear Depth Variance Chart: Note where Old and New Pinion Marking columns intersect. Intersecting figure represents plus or minus the amount needed.

PINION DEPTH MEASUREMENT (part 1):

PINION DEPTH MEASUREMENT (part 2):

PINION DEPTH MEASUREMENT





Measurements are taken with pinion bearing cups and pinion bearings installed in the housing. Take measurements with Pinion Gauge Set and Dial Indicator C3339 (1).
1. Assemble Pinion Height Block 6739 (3), Pinion Block 6736 (6) and rear pinion bearing onto Screw 6741 (5).





2. Insert assembled pinion block (1), pinion height block (2), rear bearing and screw into the housing through pinion bearing cups.
3. Install front pinion bearing and Cone-nut 6740 onto the screw. Tighten cone-nut until Torque To Rotate the screw is 2.2 Nm (20 inch lbs.).





4. Place Arbor Disc 6732 (1) on Arbor D1153 (3) in position in the housing side bearing cradles.

NOTE: Arbor Discs 6732 (1) has different step diameters to fit other axles. Choose proper step for axle being serviced.

5. Install differential bearing caps on arbor discs and snug the bearing cap bolts. Then cross tighten cap bolts to 108 Nm (80 ft. lbs.).





6. Assemble Dial Indicator C3339 (3) into Scooter Block D1152 (2) and secure set screw.
7. Position Scooter Block/Dial Indicator flush on the pinion height block. Hold scooter block and zero the dial indicator.
8. Slowly slide the scooter block across the pinion height block over to the arbor. Move the scooter block till dial indicator crests the arbor (1), then record the highest reading.
9. Select a shim equal to the dial indicator reading plus the pinion depth variance number etched in the face of the pinion. For example, if the depth variance is -2, add +0.002 inch to the dial indicator reading.

DIFFERENTIAL SIDE BEARING PRELOAD





Differential side bearing preload and gear backlash is achieved by selective shims (2) positioned behind the differential side bearing cones. The proper shim thickness can be determined using slip-fit Dummy Bearings D343 in place of the differential side bearings and a Dial Indicator C3339. Before measuring differential bearing preload and gear backlash, measure pinion gear depth and prepare pinion for installation. Pinion gear depth is essential to establishing gear backlash and tooth contact patterns. After measuring shim thickness to take up differential side play, install pinion and measure gear backlash shim thickness. Overall shim thickness is the dial indicator reading and preload specification added together. The gear backlash measurement determines the shim thickness used on the ring gear side of the differential case. Subtract gear backlash shim thickness from overall shim thickness to determine shim thickness for pinion gear side of the differential. Differential shim measurements are performed with spreader W129B removed.

SHIM SELECTION

NOTE: It is difficult to salvage the differential side bearings during the removal procedure. Install replacement bearings if necessary.

1. Remove differential side bearings from differential case.
2. Remove factory installed shims from differential case.
3. Install ring gear on differential case and tighten bolts to specification.
4. Install dummy bearings D343 on differential case.





5. Install differential case (3) in the housing (2).
6. Install the marked bearing caps (1) in their correct positions and snug the bolts.





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





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





9. Thread Pilot Stud C3288B (3) into rear cover bolt hole below ring gear.
10. Attach the Dial Indicator C3339 (4) to pilot stud. Position the dial indicator plunger on a flat surface between the ring gear bolt heads.





11. Push and hold differential case (1) to pinion gear side of the housing and zero dial indicator (4).





12. Push and hold differential case to ring gear side of the housing (3) and record the dial indicator (1) reading.
13. Add 0.38 mm (0.015 inch) to the recorded zero end play total. This total represents the thickness of shims needed to preload the new bearings when the differential is installed.
14. Rotate dial indicator out of the way on the pilot stud.
15. Remove differential case and dummy bearings from the housing.
16. Install the pinion gear in the housing. Install the pinion yoke and establish the correct pinion Torque To Rotating.





17. Install differential case (5) and dummy bearings D343 in the housing (without shims), install bearing caps and tighten bolts snug.
18. Seat ring gear side dummy bearing.
19. Position the dial indicator plunger on a flat surface between the ring gear bolt heads.
20. Push and hold differential case (5) toward pinion gear (3) and zero the dial indicator (1).





21. Push and hold differential case (5) to ring gear side (2) of the housing and record dial indicator (1) reading.
22. This is the shim thickness needed on the ring gear side of the differential case for proper backlash.
23. Subtract the backlash shim thickness from the total preload shim thickness. The remainder is the shim thickness required on the pinion side of the housing.
24. Rotate dial indicator out of the way on pilot stud.
25. Remove differential case and dummy bearings from the housing.
26. Install the selected side bearing shims onto the differential case hubs.
27. Install side bearings on differential case hubs with Install C4190 and Handle C4171.
28. Install bearing cups on differential.
29. Install Spreader W129B and some items from Adapter Set 6987 on the housing and spread open enough to receive differential case.

CAUTION: Never spread housing over 0.50 mm (0.020 inch). Failure to follow these instructions will damage the housing.

30. Install differential case into the housing.
31. Remove spreader from the housing.

GEAR BACKLASH
1. Rotate the differential case several times to seat the side bearings.





2. Position the indicator plunger (1) against a ring gear tooth.
3. Push and hold ring gear upward while not allowing the pinion gear to rotate.
4. Zero dial indicator face to pointer.





5. Push and hold ring gear downward while not allowing the pinion gear to rotate. Dial indicator reading should be between 0.12 mm (0.005 inch) and 0.20 mm (0.008 inch). If backlash is not within specifications transfer the necessary amount of shim thickness from one side of the housing to the other.
6. 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 inch). 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.

GEAR CONTACT PATTERN
The ring gear and pinion teeth contact patterns will show if the pinion depth is correct in the axle 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.





NOTE: If the PROFILE across the gear tooth is the same it is a 3 Axis cut gear. If the PROFILE across the gear tooth is tapered it is a 2 Axis cut gear.

1. Apply a thin coat of hydrated ferric oxide or equivalent, to the drive and coast side of the ring gear teeth.
2. 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.
3. Using a boxed end wrench on a 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 and adjust pinion depth and gear backlash as necessary

DIFFERENTIAL BEARING PRELOAD CHECK
The final check on the differential assembly before installing the axles is torque to rotate pinion and differential combined. This will verify the correct differential bearing preload.
Total Torque to Rotate the differential is: Pinion Torque to Rotate plus 0.33 to 0.56 Nm (3 to 5 inch lbs.).