525B Wheel Skidder and 535B Wheel Skidder Power Train Caterpillar

Note: The procedure gives the same results for new bearings and for used bearings. The following procedure is used for the front differential and the rear differential.

Illustration 1	g00722596
Bevel Gear and Pinion (Differential) (1) Bearing sleeve (2) Bolt. (3) Adjusting nut (4) Bearing cone (5) Bearing cup (6) Pin (7) Piston (8) O-ring seal on piston (9) Needle bearing (10) Thrust ring (11) Pinion housing (12) Adjusting nut (13) Pinion (14) Intermediate housing (15) Dowel (16) Differential group (17) Bevel gear (18) Bolt (19) Bearing sleeve (20) Bolt (21) Bearing cup (22) Bearing cone (23) Adjusting nut (24) Pin (25) Center housing (26) Shims (27) O-ring seal on pinion housing

The following procedure is used to assemble differential group (16) .

1. Heat bevel gear (17) to 135° C (275° F) for a maximum of four hours. Install the bevel gear on differential group (16) .

   Note: The bevel gear must be attached to the differential gear case, prior to the differential component assembly.

2. Allow bevel gear (17) to cool to room temperature, before you tighten the bolts. Tighten 20 bolts (18) for the front bevel gear to the specified torque 270 ± 40 N·m (200 ± 30 lb ft). Tighten 20 bolts (18) for the rear bevel gear to the specified torque 270 ± 40 N·m (200 ± 30 lb ft). Check that bevel gear (17) is properly seated on the shoulder of differential group (16) .

3. Press bearing cone (4) and bearing cone (22) on the differential case. Make sure that the bearing cones are fully seated.

   Note: If you freeze the bearing cups, allow mating 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 30 gear oil in order to prevent rust.

   Note: If you heat the bearing cones, allow mating 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 30 gear oil after the bearing cones have cooled in order to prevent rust.

4. Remove intermediate housing (14) from center housing (25) .

5. Install bearing cup (21) into bearing sleeve (19). Install bearing sleeve (19) and pin (24) in center housing (25). Lubricate the threads of adjusting nut (23) and install the nut into center housing (25) .

6. Position center housing (25) in an appropriate supporting fixture so that the open side faces upward. Use a lifting device to lower differential group (16) and bevel gear (17) into position in center housing (25). The bevel gear will be adjacent bearing cup (21) .

7. Lubricate needle bearing (9) with SAE 30 gear oil. Install needle bearing (9) onto the thrust ring (10) .

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Illustration 2	g00727539
Differential (7) Piston. (8) O-ring seals. (A) Dimension.

8. Install two dowel pins 19.5 ± 1.0 mm (.768 ± .039 inch) (A) in the differential lock piston. Install two O-ring seals (8) on piston (7). Lubricate O-ring seals (8) with petroleum jelly. Lubricate the piston bore with petroleum jelly. Install the piston evenly into intermediate housing (14). This will prevent seal damage.

   Note: Use only petroleum jelly for lubrication.

9. Apply 1U-8846 Sealant on center housing (25). Use dowel pins (15) in order to reinstall intermediate housing (14) on center housing (25). Install four bolts and torque four bolts to 100 ± 20 N·m (75 ± 15 lb ft).

10. Install bearing cup (5) into bearing sleeve (1). Install bearing sleeve (1) and pin (6) in intermediate housing (14). Lubricate the threads of adjusting nut (3) and install the nut into intermediate housing (14) .

11. Lubricate O-ring seal (27) and install O-ring seal (27) on pinion housing (11). Install pinion housing (11) on center housing (25). To install the pinion housing for the front differential and the rear differential, install ten bolts and torque to 300 ± 40 N·m (220 ± 30 lb ft). Use the original thickness of shims (26) or use a new shim pack that is measured to the same thickness as the original shim pack. If the original shim pack is not available, use 70 percent of a new shim pack.

    Note: The required thickness of the shim pack may change when the tooth contact pattern is adjusted. See the section "Pinion and Bevel Gear Tooth Contact Check" for the correct tooth contact pattern.

12. Reposition center housing (25) in the supporting fixture so that center housing (25) and pinion housing (11) are horizontal. This is the same position as if the parts are installed in the machine.

13. Tighten adjusting nuts (3) and (23) to a position that maintains gear backlash and slight bearing end play. This position should not maintain tight gear mesh.

14. Use the torque measurement that was recorded in the "Differential Pinion Preload - Adjust" section.

15. While you rotate pinion shaft (13) back and forth, tighten adjusting nut (23) to the zero backlash position. Then back off adjusting nut (23) by 20 degrees plus the increment to the nearest lock position.

16. Tighten adjusting nut (3), while you rotate pinion shaft (13). Adjust the torque value until the value equals Step 14 plus 3.2 ± 0.5 N·m (28.5 ± 4.5 lb in). This is the seated position.

    Note: As a check for the correct assembly and for the correct adjustment, the rolling torque of the differential and bevel gear group at the shaft of the pinion should be 3.4 to 5.6 N·m (30 to 50 lb in) for new bearings. For used bearings, the rolling torque should be 1.7 to 2.8 N·m (15 to 25 lb in).

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Illustration 3	g00275111
Pinion Shaft Spline (backlash measurement) (B) Distance of dial indicator from the centerline of the pinion.

17. Measure the backlash between bevel gear (17) and pinion shaft (13) on the pinion shaft spline. To measure the backlash, place a dial indicator tangent to the spline on a flat of a drive shaft yoke or a spline adapter. Make sure that the yoke or the spline adapter is tight to the spline.

18. The following table lists examples of backlash at the pinion shaft. The table shows the different distances from the centerline of the pinion to the dial indicator:
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    Table 1

    Examples of Backlash at Pinion Shaft
    Dimension (B)	Nominal Backlash	Maximum Backlash	Minimum Backlash
    50 mm (2 inch)	0.30 mm (.012 inch)	0.40 mm (.016 inch)	0.18 mm (.007 inch)
    100 mm (4 inch)	0.58 mm (.023 inch)	0.80 mm (.032 inch)	0.35 mm (.014 inch)
    150 mm (6 inch)	0.87 mm (.035 inch)	1.20 mm (.048 inch)	0.53 mm (.021 inch)
    200 mm (8 inch)	1.15 mm (.046 inch)	1.60 mm (.064 inch)	0.70 mm (.028 inch)

    If the backlash does not meet specifications, loosen one adjusting nut and tighten the opposite adjusting nut by the same amount. This will maintain the bearing preload.

Check the Pinion and Bevel Gear Tooth Contact

1. After the differential backlash adjustments and the pinion preload adjustments have been made, check the tooth contact between pinion shaft (13) and bevel gear (17). Perform the following procedure:

   1. Coat three or four adjacent teeth of bevel gear (17) with a rouge compound.

   2. Rotate pinion shaft (13) for several revolutions in one direction. Then rotate pinion shaft (13) for several revolutions in the opposite direction. Then turn the pinion shaft in one direction until the marked teeth can be viewed.
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   Illustration 4	g00103470

   3. The correct area of tooth contact begins near the inside end of the teeth of bevel gear (17). The correct area extends 25 to 50 percent of the tooth length. See Illustration 4 for an example of the correct area of tooth contact.
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   Illustration 5	g00103471

   4. If the tooth contact looks like the marks in Illustration 5, remove some of shims (26) and check the backlash again. Repeat the procedure under Step 1.
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   Illustration 6	g00508806

   5. If the tooth contact looks like the marks in Illustration 6, add some of shims (26) and check the backlash again. Repeat the procedure under Step 1.

Note: Always make sure that the backlash adjustment is correct before an adjustment is made to the area of tooth contact. To achieve the correct adjustments, the backlash and the tooth contact may need to be adjusted several times. Always remember that a change to gear clearance (backlash) will also change the gear contact and vice versa.

2. After adjustments are made, remove the rouge compound from the gears.

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Illustration 7	g00572825
(2) Bolt. (3) Adjusting nut.

3. Install bolt (2) and a lock tab washer in adjusting nut (3). Tighten bolt (2) to 12 ± 3 N·m (9 ± 2 lb ft) and then bend the lock tab washer onto the flats of the bolt. See Illustration 7.

4. Repeat Step 3 for bolt (20) and adjusting nut (23) on the opposite end of differential.