918F WHEEL LOADER POWER TRAIN Caterpillar


Differentials & Pinion

Usage:

Remove & Install Differentials & Pinion Assemblies

Start By:

a. remove front axle housing group (fixed)

b. remove rear axle housing group (oscillating)

1. Remove one of the brake groups from the axle housing group. See the topic, "Remove & Install Brake Groups" in this module.

2. Fasten a hoist to intermediate housing assembly (1) as shown. Remove the four bolts that hold intermediate housing assembly (1) to the differential center housing. Remove the intermediate housing assembly. The weight of the intermediate housing assembly is approximately 57 kg (125 lb).

3. Remove bolt (2) and washer (3).

NOTE: Two different size adjusting nuts are used in the bevel gear group. Use Tool (E) or (F) to remove the appropriate size adjusting nuts.

4. Use the appropriate Tool, (E) or (F), to remove adjusting nut (4). Remove the pin, sleeve (6) and bearing cup (7) from intermediate housing assembly (1).

5. Remove two of the bolts (8), located 180° apart from each other, that hold the pinion assembly to the differential center housing. Install two suitable size guide bolts that are approximately 152.4 mm (6.00 inch) long in the bolt holes as shown.

6. Remove the remaining bolts (8) that hold the pinion assembly to the differential center housing. Slide the pinion out on the guide bolts far enough to install Tool (A). Fasten a hoist to the pinion assembly as shown.

7. Remove the pinion assembly from the differential center housing. The weight of the pinion assembly is approximately 66 kg (145 lb). Remove the shims and O-ring seal from the pinion housing.

8. Fasten Tool (A) and a hoist to the differential as shown. Carefully lift the differential out of the differential center housing. The weight of the differential is approximately 109 kg (240 lb).

9. Turn the remainder of the axle housing group over, and fasten it to the transmission repair stand. Fasten Tool (B) and a hoist to the rim flange on axle shaft assembly (9) as shown. Remove twenty six bolts (10) and the washers that hold the axle shaft assembly to the differential center housing. Remove the axle shaft assembly. The weight of the axle shaft assembly is approximately 295 kg (650 lb).

10. Remove the brake group from the differential center housing. See "Remove & Install Brake Groups" in this module.

11. Repeat Steps 2 through 4 to remove and disassemble the other intermediate housing assembly (1) that is on the differential center housing.

12. Remove bearing cone (11) from the differential with tool (C).

13. Turn the differential over, and remove bearing cone (12) with Tool (D).

14. Use a press to remove the four large spring pins and four small spring pins (13) from the differential.

15. Remove twenty bolts (14) that hold bevel gear (15) in position. Using a press, remove bevel gear (15) from the differential.

NOTE: The following procedure is for the installation of the differential and pinion assembly. Also, the following procedure controls bearing preload and gives the same results for new or used bearings.

16. Heat bevel gear (15) to a temperature of 135°C (275°) for a maximum of four hours. Install the bevel gear on the differential.

17. Install four large pins (13) partially into bevel gear (15). Install four small pins (13) into the large pins. Press the pins into bevel gear (15) until they are even with the outside surface of the bevel gear. Install twenty bolts (14) that hold the bevel gear to the differential. Tighten bolts (14) to a torque of 95 ± 10 N·m (70 ± 7 lb ft). Tighten each bolt an additional 180 ± 5°. Check to be sure the bevel gear is seated on the differential group shoulder.

18. Press bearing cone (11) and bearing cone (12) on the differential case. Check for full seating of the bearing cones.

NOTE: Cup freezing or cone heating may be used if cups or cones are reset with a driver or press after the parts have reached a uniform temperature. Limit cone heating to 135°C (275°F) maximum for a maximum of 4 hours. Lubricate the bearings after they have cooled to prevent rusting.

19. Install bearing cup (7), sleeve (6) and the pinion in the intermediate housing. Lubricate the threads on adjusting nut (4), and install it in intermediate housing assembly (1).

20. Assemble the other intermediate housing (1) as in Step 19.

21. Position the differential center housing on a transmission repair stand with the open side facing upward. Fasten Tool (A) and a hoist to the differential, and lower it on to the three dowels in the differential center housing.

22. Fasten a hoist to intermediate housing assembly (1). Install the intermediate housing assembly on the differential center housing. Install and tighten the four bolts that hold it.

NOTE: Use the original thickness of shims or a new shim pack measured to the same thickness as the original pack. If the original shim pack is not available, use 60% of a new shim pack.

23. Lubricate and install the O-ring seal used on the pinion housing. Install the original shim pack on the pinion housing. Install the two guide bolts in the differential center housing. Fasten tool (A) and a hoist to the pinion assembly, and install it in the differential center housing. Install twelve bolts (8) that hold the pinion assembly in position. Tighten the bolts to a torque of 300 ± 40 N·m (220 ± 30 lb ft).

NOTE: The shim pack thickness may have to be changed when adjusting the tooth contact pattern between the bevel gear and pinion shaft.

24. Reposition the differential center housing on the transmission repair stand so the differential center housing and the pinion assembly are horizontal (the same position) as they are in the vehicle).

25. Tighten adjusting nuts (4) and (26) with tooling (E) and (F) to a position that maintains gear backlash (but not tight gear mesh) and a slight bearing end play.

26. Measure the torque required to rotate the pinion shaft. Record the measured torque. Use a 1U-6690 Socket on the pinion shaft nut for this measurement.

27. While rotating the pinion shaft back and forth, tighten adjusting nut (26) to zero backlash position. Then back off adjusting nut (26) 20°.

28. Tighten adjusting nut (4) while rotating the pinion shaft. Tighten nut (4) until a torque increase of 0.2 to 0.6 N·m (2.0 to 5.0 lb inch) over the torque recorded in Step 26 is measured. This is the bearing seated position.

29. Tighten adjusting nut (4) 40° plus the increment to the nearest lock position.



Pinion Shaft Spline (backlash measurement)

(A) Distance of dial indicator from pinion centerline.

NOTE: As a check for the correct assembly and adjustment, the rolling torque of the bevel gear group measured at the pinion shaft should be 1.8 to 3.6N·m (16 to 32 lb inch) for new bearings and 0.9 to 1.8 N·m (8 to 16 lb inch) for used bearings.

30. Measure the backlash between bevel gear (15) and the pinion shaft. The backlash must be 0.30 + 0.12 - 0.10 mm (.011 + .005 - .004 inch). Do this by placing a dial indicator (as shown) tangent to the spline, making sure the yoke or spline adapter is tight to the spline.

31. The following chart gives examples of backlash at the pinion shaft, by showing the different distances from the pinion centerline to the dial indicator:

32. If the backlash does not meet specifications, loosen one adjusting nut the same amount as the opposite adjusting nut is tightened. This will maintain the bearing preload.


Illustration A

33. After the backlash and preload adjustments have been made, the tooth contact between pinion shaft and bevel gear (15) must be checked. Do the procedure that follows:

a. Put a small amount of Prussian blue, red lead or paint on three or four adjacent teeth of bevel gear (15).
b. Rotate the pinion shaft several revolutions in one direction and then several revolutions in the opposite direction. Then turn the pinion shaft in one direction until the marked teeth can be seen.
c. The correct area of tooth contact starts near the inside end of the teeth of bevel gear (15) and goes a maximum of 50% of the length of the teeth. See Illustration A for an example of the correct area of tooth contact.


Illustration B

34. If the tooth contact looks like the marks in Illustration B, do the procedure that follows:

a. Remove some of the shims from behind the pinion housing.
b. Do Steps 29, 30 and 31 for the backlash adjustment procedure again.
c. Do Step 32 again.


Illustration C

35. If the tooth contact looks like the marks in Illustration C, do the procedure that follows:

a. Add shims behind the pinion housing.
b. Do Steps 29, 30 and 31 again.
c. Do Step 32 again.

NOTE: Always be sure the backlash adjustment is correct before an adjustment is made to the area of tooth contact. Several adjustments to the backlash and tooth contact may be necessary to get the correct adjustments. Always remember that a change to gear clearance (backlash) will also change the gear contact. A change in gear contact will also change gear clearance (backlash).

36. After adjustments are made, remove the Prussian blue, red lead or paint from the gears.

37. Install one bolt and lock (2) in each adjusting nut (4) and (26), tighten both bolts and bend the locks.

38. Install the brake groups and the axel shaft assemblies on the differential center housing. See the topic, "Remove & Install Brake Groups" and "Disassemble & Assemble Axle Shaft Assemblies" in this module.

End By:

a. install rear axle housing group (oscillating)

b. install front axle housing group (fixed)

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