Rear Axle - 226RBI

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).





Compensation for pinion depth variance is achieved with select shims (1). The shims are located between the rear pinion bearing and pinion gear head.

When 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 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





Measurements are taken with pinion bearing cups and pinion bearings installed in the housing. Take measurements with Pinion Gauge Set 6730 and Dial Indicator C-3339A (1).

1. Assemble Pinion Height Block 6739 (3), Pinion Block 9792 (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 in. lbs.).




4. Place Arbor Disc 9795 (1) on Arbor D-115-3 (3) in position in the housing side bearing cradles.




5. Install differential bearing caps (1) on arbor discs (2) and install bearing cap bolts. Cross tighten cap bolts to 108 Nm (80 ft. lbs.).




6. Assemble Dial Indicator C-3339A (1) into Scooter Block D-115-2A (2) and secure set screw.
7. Position scooter block with dial Indicator flush on the pinion height block. Hold scooter block and zero the dial indicator.
8. Slowly slide the scooter block up 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 or minus the pinion depth variance number etched in the face of the pinion. For 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.

DIFFERENTIAL SIDE BEARING PRELOAD





Before measuring differential bearing preload and gear backlash, measure pinion gear depth and prepare pinion gear for installation. Pinion gear depth is essential to establishing gear backlash and tooth contact patterns.

Differential side bearing preload and gear backlash is achieved by selective shims (2) positioned between the differential side bearing cups and housing. The proper shim thickness is determined using, Dummy Bearings 9794 in place of the differential side bearings and shims. The dummy bearings have 2.1 mm (0.085 in.) added to each bearing, this eliminates the need for dummy shims.

SHIM FORMULA : Differential End Play + Preload Specification + 4.3 mm (0.170 in.) - Ring Gear Side Shim - Backlash Specification = Pinon Gear Side Shim

SHIM SELECTION





1. Remove differential side bearings from differential case.
2. Install Dummy Bearings 9794 on differential case (3).
3. Install differential case (3) in the housing (2).
4. Install marked bearing caps (1) in their correct positions and snug the bolts.




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




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




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




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




10. Push and hold differential case (2) to ring gear side of the housing and record differential dial indicator (1) reading.
11. Add 4.3 mm (0.170 in.) plus, preload specification 0.38 mm (0.015 in.) to the differential end play reading. This represents the total shim thickness needed to preload the differential bearings.
EXAMPLE: Differential Dial Indicator Reading + 4.3 mm (0.170 in.) + Preload Specification 0.38 mm (0.015 in.) = Total Differential Shim

12. Rotate dial indicator out of the way on the pilot stud.
13. Remove differential case and dummy bearings from the housing.
14. Install pinion gear in the housing and establish Pinion Torque To Rotating.




15. Install differential case with Dummy Bearings 9794 into the housing. Install bearing caps and tighten bolts snug.
16. Seat ring gear side dummy bearing.
17. Position dial indicator plunger on a flat surface between the ring gear bolt heads.
18. Push and hold differential case (1) to pinion gear side of the housing and zero the dial indicator (2).




19. Push and hold differential case (2) to ring gear side of the housing. Record ring gear side dial indicator (1) reading.
20. Add 2.1 mm (0.085 in.) to ring gear side reading then subtract backlash specification 0.05 mm (0.002 in.). This is the shim needed for the ring gear side of the differential.
EXAMPLE: Ring Gear Side Dial Indicator Reading + 2.1 mm (0.085 in.) - Backlash Specification 0.05 mm (0.002 in.) = Ring Gear Side Shim

21. Subtract ring gear side shim from the total shim thickness. The is the shim needed on the pinion side of the differential.
EXAMPLE : Total Differential Shim - Ring Gear Side Shim = Pinion Gear Side Shim

22. Rotate dial indicator (1) out of the way on pilot stud.
23. Remove differential case and dummy bearings from the housing.




24. Install differential side bearings on differential case.
25. Install Spreader W-129-B (1) and some items from Adapter Set 6987B (2) on the housing and spread open enough to receive differential case.

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





26. Install differential case (2) with bearing cups (3) and shims into the housing (1).
27. Install differential case bearing caps.
28. Remove spreader from the housing.
29. Tighten bearing caps to specification.

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 0.15 to 0.20 mm (0.006 to 0.008 in.).
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 in.). If readings vary more than specified, the ring gear or the differential case is defective.




7. If backlash is not within specifications, transfer the necessary amount of shim thickness from one side of the housing to the other.
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 (TTTR ) the differential is: Pinion Torque To Rotate plus 0.44 to 1.34 Nm (4 to 12 in. lbs.).

If TTTR is too high, decrease shim thickness equally from both sides of the differential and check TTTR again. If TTTR is too low, increase shim thickness equally to both sides of the differential and check TTTR again.