990K Wheel Loader Machine Systems Caterpillar

Specifications

Illustration 1	g00405449
Differential and Bevel Gear (1) Adjusting nut lock (2) Bolts (3) Adjusting nut (4) Bolts (5) Cover (6) Shims (7) Pin (8) Bearing cup (9) Bearing cone (10) Shims (11) Bevel gear (12) Housing (13) Bearing cup (14) Bearing cone (15) Retainer (16) Bolts (17) Adjusting nut lock (18) Adjusting nut (19) Differential case (20) Bolts (21) Differential (22) Bearing cone (23) Bearing cup (24) Carrier assembly (25) Bearing cup (26) Bearing cone (27) Washer (28) Nut (29) Bevel pinion

Introduction

Note: The following procedure controls bearing preload. The procedure provides the same results for new bearings and for used bearings.

Adjustment Procedure

1. Install bevel gear (11) onto differential case (19). Torque for the 36 bolts is 750 ± 90 N·m (550 ± 65 lb ft).

2. Install bearing cone (9) and bearing cone (22) onto differential group (21). Make sure that the bearing cone is fully seated. Lubricate the bearing cone with SAE 50W differential oil.

3. Press bearing cup (13) and bearing cup (25) on pinion housing (12). Make sure that the bearing cups are fully seated.

4. Press bearing cone (14) on pinion (29). Make sure that the bearing cone is fully seated. Lubricate the bearing cone with SAE 50W differential oil.

5. Install pinion (29) in housing (12). Press bearing cone (26) onto the pinion shaft. Allow a small amount of end play to remain. Lubricate the bearing cone with SAE 50W differential oil.

   Note: If you freeze the bearing cups, allow the parts to reach a uniform temperature. Then use a driver or a press to reset the bearing cups. The limit for freezing the bearing cups is −29°C (−20°F). Remove any frost and wipe the bearing cups dry. Lubricate the bearing cups with SAE 50W differential oil in order to prevent rust on the bearing cups.

   Note: If you heat the bearing cones, allow the parts to reach a uniform temperature. Then use a driver or a press to reset the bearing cones. The limit for heating the bearing cones is a maximum of 135°C (275°F) for a maximum of four hours. Lubricate the bearing cones with SAE 50W differential oil after the bearing cones have cooled in order to prevent rust on the bearing cones.

6. Secure the assembled pinion housing (12) in a holding fixture. Install washer (27) and nut (28).
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   Table 1

   Required Tools
   Part Number	Description	Quantity
   1U-6691	Socket Wrench Assembly	1

7. While you rotate pinion shaft (29), tighten nut (28) in order to achieve a preload rolling torque of 2.2 to 5.1 N·m (20 to 45 lb in). This is the torque that is needed in order to rotate pinion (29). Make sure that there is zero end play of pinion shaft (29).

   Note: Reduce preload rolling torque to 1.1 to 2.55 N·m (10 to 23 lb in) for used roller bearings with more than 100 hours of operation.

8. If the preload rolling torque for the pinion exceeds the specifications, back off nut (28) by 1/8 turn and reseat bearing cone (26) and washer (27) against nut (28). Perform Step 7 again.
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   Illustration 2	g00103469
   Stake Nut and Tooling

9. When the torque for rotating pinion (29) is correct, stake nut (28) by peening the collar into the slot in the pinion shaft. Proper peening requires the use of a punch with a spherical nose. The punch should have a nose that is (C) diameter. The punch should be held at an angle (B). The desired result is a stake of minimum length (D) and minimum depth (E). See Illustration 2 for a view of a completed staked nut.

   List of dimensions for a staked nut

   Dimension (B) ... 10 to 30°

   Dimension (C) ... 7.5 to 8.0 mm (0.30 to 0.32 inch)

   Dimension (D) ... 4.7 mm (0.19 inch)

   Dimension (E) ... 2.5 mm (0.10 inch)

   Note: The nut may be reused if the collar is not cracked during removal or during restaking.

10. Secure carrier assembly (24) in a holding fixture.

11. Install the pinion subassembly in carrier assembly (24) with 80 percent of a new shim pack (10). Make sure that the axle centerline is vertical and that the teeth of bevel gear (11) are facing upward, as shown.

12. Tighten bolts (2) and (16) in each bearing cap to a torque of 25 N·m (18 lb ft).

13. Move adjusting nut (3) and adjusting nut (18) to a position that maintains the gear backlash and a slight bearing end play, but not a tight gear mesh.

14. Reposition the differential assembly so that the pinion shaft is vertical and the gear end is downward.

15. Measure the torque for rotating pinion (29) and record the measured torque.

16. Move adjusting nut (3) to the zero backlash position. Back off adjusting nut (3) by one-half turn.

17. Move adjusting nut (18) while you rotate bevel gear (11). Monitor the torque that is required to rotate pinion (29).

18. Continue to move adjusting nut (18) until a torque is registered over the torque that was measured in Step 15. This is the seated position.

19. Move adjusting nut (18) while rotating the bevel gear set until the overall rolling torque is 4 N·m to 15 N·m (35 lb in to 130 lb in).

20. Measure the backlash between bevel gear (11) and pinion gear (29). Measure the backlash at three equally spaced positions around the bevel gear. The backlash must be 0.40 ± 0.12 mm (0.016 ± 0.005 inch).

21. If the backlash does not meet the specification at any one of the three positions, back off one adjusting nut and move the other adjusting nut forward by the same amount. This will maintain the bearing preload.

22. Measure the torque for rotating pinion (29). The torque must be 4 N·m to 15 N·m (35 lb in to 130 lb in).

23. When proper backlash has been obtained tighten bolts (2) and (16) in each bearing cap to a torque of 1800 ± 200 N·m (1330 ± 150 lb ft).

24. Install adjusting nut locks (1) and (17).

Tooth Contact Pattern Adjustment (Pinion and Bevel Gear)

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Illustration 3	g00103470

1. After the backlash adjustment and the preload adjustment have been made, check the tooth contact between pinion (29) and bevel gear (11) by using the following procedure:

   1. Put a small amount of Prussian blue, of red lead, or of paint on the teeth of bevel gear (11).

   2. Turn pinion (29) in both directions.

   3. The end of the correct area of tooth contact is near the inside end of the teeth of the bevel gear (11). The contact area should extend halfway across the length of the teeth. See Illustration 3 for the correct area of tooth contact.
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   Illustration 4	g00103471

2. If the area of tooth contact looks like Illustration 4, use the following procedure:

   1. Remove some of the shims (10).

   2. Perform Step 14 through Step 24 again.

   3. Perform Step 2 and Step 3 again in order to check the area of tooth contact.
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   Illustration 5	g00103472

3. If the area of tooth contact looks like Illustration 5, use the following procedure:

   1. Add some of the shims (10).

   2. Perform Step 14 through Step 24 again.

   3. Perform Step 2 and Step 3 again in order to check the area of tooth contact.

      Note: Always make sure that the backlash adjustment is correct before an adjustment is made to the area of tooth contact. Several adjustments to the backlash and to the tooth contact may be necessary in order to achieve the correct adjustments.

4. Install pin (7) and cover (5) without shims (6). Tighten bolts (4) enough in order to remove any clearance between the pin and the cover.

5. Measure the distance between the face of the cover (5) and the face of the axle housing. Install the shims (6) so that the pin is under a preload of −0.03 mm (−.001 inch) or an end play of 0.03 mm (.001 inch).

6. Install retainer (15).