Rear Axle - 194RBI
REAR AXLE - 194RBIADJUSTMENTS
RING AND PINION GEAR
Ring and pinion gears are supplied as matched sets only. The identifying numbers for the ring and pinion gear are etched into the face of each gear (Fig. 6). A plus (+) number, minus (-) number or zero (0) is etched into the face of the pinion gear. 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 teeth contact pattern.
Compensation for pinion depth variance is achieved with select shims. The shims are placed under the inner pinion bearing cone (Fig. 7).
If a new gear set is being installed, note the depth variance etched into both the original and replacement pinion gear. Add or subtract the thickness of the original depth shims to compensate for the difference in the depth variances. Refer to the Depth Variance charts.
Note where Old and New Pinion Marking columns intersect. Intersecting figure represents plus or minus amount needed.
Note the etched number on the face of the drive pinion gear (-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 shim(s). If the number is positive, subtract that value from the thickness of the depth shim(s). If the number is 0 no change is necessary. Refer to the Pinion Gear Depth Variance Chart.
PINION GEAR DEPTH VARIANCE
PINION DEPTH MEASUREMENT
Measurements are taken with pinion cups and pinion bearings installed in the housing. Take measurements with a Pinion Gauge Set, Pinion Block 6735, Arbor Discs 6732 and Dial Indicator C-3339 (Fig. 8).
1. Assemble Pinion Height Block 6739, Pinion Block 6735 and rear pinion bearing onto Screw 6741 (Fig. 8).
2. Insert assembled height gauge components, rear bearing and screw into the housing through pinion bearing cups (Fig. 9).
3. Install front pinion bearing and Cone 6740 hand tight.
4. Place Arbor Disc 6732 on Arbor D-115-3 in position in the housing side bearing cradles (Fig. 10). Install differential bearing caps on Arbor Discs and tighten cap bolts. Refer to the Torque Specifications.
NOTE: Arbor Discs 6732 have different step diameters to fit other axle sizes. Pick correct size step for axle being serviced.
5. Assemble Dial Indicator C-3339 into Scooter Block D-115-2 and secure set screw.
6. Position Scooter Block/Dial Indicator flush on the pinion height block. Hold scooter block and zero the dial indicator.
7. Slowly slide the scooter block across the pinion height block over to the arbor (Fig. 11). Move the scooter block till the dial indicator probe crests the arbor, then record the highest reading.
8. Select a shim equal to the dial indicator reading plus the drive pinion gear depth variance number etched in the face of the pinion gear (Fig. 6) using the opposite sign on the variance number. For example, if the depth variance is -2, add +0.002 inch to the dial indicator reading.
9. Remove the pinion depth gauge components from the housing
DIFFERENTIAL BEARING PRELOAD
Differential side bearing preload and gear backlash is achieved by selective shims inserted between the bearing cup and the housing. The proper shim thickness can be determined using slip-fit Dummy Bearings D-348 in place of the differential side bearings and a Dial Indicator C-3339. Before proceeding with the differential bearing preload and gear backlash measurements, measure the pinion gear depth and prepare the pinion gear for installation. Establishing proper pinion gear depth is essential to establishing gear backlash and tooth contact patterns. After the overall shim thickness to take up differential side play is measured, the pinion gear is installed and the gear backlash shim thickness is measured. The overall shim thickness is the total of the dial indicator reading, starting point shim thickness and the preload specification added together. The gear backlash measurement determines the thickness of the shim used on the ring gear side of the differential case. Subtract the gear backlash shim thickness from the total overall shim thickness and select that amount for the pinion gear side of the differential (Fig. 12).
PRELOAD SHIM SELECTION
NOTE: It is difficult to salvage the differential side bearings during the removal procedure. Install replacement bearings if necessary.
1. Remove side bearings from differential case.
2. Install ring gear, if necessary, on differential case and tighten bolts to specification.
3. Install Dummy Bearings D-348 on differential case.
4. Install differential case in the housing.
5. Insert Dummy Shims 8107 (3.0 mm / 0.118 inch) starting point shims between the dummy bearing and the housing (Fig. 13).
6. Install bearing caps in their correct positions and snug the bolts.
7. Using a dead-blow hammer to seat the differential dummy bearings to each side of the housing (Fig. 14) and (Fig. 15).
8. Thread Pilot Stud C-3288-B into rear cover bolt hole below ring gear (Fig. 16).
9. Attach Dial Indicator C-3339 to the pilot stud and position indicator plunger on a flat surface of the ring gear bolt head (Fig. 16).
10. Push differential case to the pinion gear side of the housing (Fig. 17) and zero dial indicator.
11. Push differential case to the ring gear side and record dial indicator reading (Fig. 18).
12. Add the dial indicator reading to the starting point shim thickness to determine total shim thickness to achieve zero differential end play.
13. Add 0.008 inch (0.2 mm) to the zero end play total. This new total represents the thickness of shims to compress or preload the new bearings when the differential is installed.
14. Rotate dial indicator out of the way.
15. Remove differential case, dummy bearings and starting point shims from the housing.
16. Install pinion gear in the housing. Install the yoke and establish the correct pinion rotating torque.
17. Install differential case and dummy bearings in the housing (without shims) and tighten retaining cap bolts.
18. Position the dial indicator plunger on a flat surface between the ring gear bolt heads (Fig. 16).
19. Push and hold differential case toward pinion gear.
20. Zero dial indicator face to pointer.
21. Push and hold differential case to ring gear side of the housing and record dial indicator reading.
22. Subtract 0.002 inch (0.05 mm) from the dial indicator reading to compensate for backlash between ring and pinion gears. This total is the thickness of shim required to achieve 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 new side bearing cones and cups on differential case.
27. Install spreader W-129-B and some components of Adapter Set 6987 on differential housing and spread axle opening enough to receive differential case.
28. Place side bearing shims into the housing against the differential bearing bore.
29. Install differential case in the housing.
30. Rotate the differential case several times to seat the side bearings.
31. Position the indicator plunger against a ring gear tooth (Fig. 19).
32. Push and hold ring gear upward while not allowing the pinion gear to rotate.
33. Zero dial indicator face to pointer.
34. 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 inch - 0.008 inch). If backlash is not within specifications transfer the necessary amount of shim thickness from one side of the differential housing to the other (Fig. 20).
35. 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 the 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 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 of the gear tooth is the top surface of the tooth. The PROFILE of the gear tooth is the depth of the tooth. The TOE of the gear is the portion of the tooth surface at the end towards the center. The HEEL of the gear is the portion of the tooth at the outer-end. The ROOT of the gear tooth is the lowest portion of the tooth (Fig. 21).
NOTE: 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 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. With 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 squeeze 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 charts (Fig. 22) and (Fig. 23) 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.
Torque to rotate the differential and pinion should be the torque to rotate the pinion plus 0.79 - 1.24 Nm (7 - 11 inch lbs.).