2000/04/17 Caterpillar

Off-Highway Truck/Tractor:

784B (S/N: 5RK1-UP)

784C (S/N: 2PZ1-UP)

785 (S/N: 8GB1-UP)

785B (S/N: 6HK1-UP)

785C (S/N: 1HW1-UP; APX1-UP)

785C HAA (S/N: 5AZ1-UP)

789 (S/N: 9ZC1-UP)

789B (S/N: 7EK1-UP)

789C (S/N: 2BW1-UP)

793 (S/N: 3SJ1-UP)

793B (S/N: 1HL1-UP)

793C (S/N: 4AR1-UP; ATY1-UP; 4GZ1-UP)

This article replaces the previous article that was printed.

Note: The following article replaces all previous wheel bearing adjustment procedures for cast wheels and fabricated wheels for the listed off-highway trucks.

The new vertical wheel adjustment procedure for the following off-highway trucks has been improved: 793, 793B, 793C, 789, 789B, 789C, 785, 784B/785B and 784C/785C.

The procedure for setting the rear wheel bearing preload in the horizontal position has been eliminated for the listed off-highway trucks.

There should be no adjustment to the shim pack when the existing wheel bearings are reused during the following repair procedures: replacement of the duo-cone seals and repair of the brakes on the wheel group assembly. The existing shim pack should be reused.

The procedures for setting the wheel bearing preload in this article must be performed in the vertical position in order to achieve accurate results. If the wheel brake assembly is installed, the parking brake must be released. Make sure that the wheel bearing cups are fully seated against the face of the bore in the wheel. Use a 0.05 mm (0.002 inch) feeler gauge to check the gap between the bearing cup and the face of the bore in the wheel. The wheel bearing cones should slide freely over the spindle. Tighten the bolts in a crisscross pattern.

Vertical Wheel Bearing Adjustment Procedure For Cast Wheels And Fabricated Wheels Of The 793, 793B And 793C Off-Highway Trucks Which Use High Capacity Bearings

Illustration 1	g00659584
This is a typical cross section view of a wheel group assembly. (A) Tapped hole (1) Cup (2) Cone (3) Shim Pack (4) Retainer (5) Bolts (6) Washers

Illustration 2	g00659589
Area (C) The gap is determined by the dimension (C) minus the dimension (B) .

Illustration 3	g00664274
View (B-B) Sequence for the initial tightening procedure (D) Bolt (E) Bolt (F) Bolt (4) Retainer

Use the following procedure to adjust the wheel bearings.

1. Clean the tapped holes (A) in the end of the spindle in order to receive the bolts for the retainer (4) .

2. Use an outside micrometer to measure the thickness of the retainer (4). Measure the thickness near the bolt holes in three different locations. Average the three dimensions and record the average as dimension (B). Refer to Illustration 2.

3. Ensure that the following parts are installed correctly: cup (1), cone (2) and reaction hub. Use three NEW bolts (5) in order to install retainer (4) on the spindle. Install the NEW bolts into holes that are equally spaced in the following positions: (D), (E) and (F). Refer to Illustration 1 and Illustration 3.

4. Release the brakes.

   Note: The oil pressure that is required to release the brakes is approximately 4690 ± 200 kPa (680 ± 29 psi).

5. Tighten the three NEW bolts (5) in a clockwise bolt tightening sequence : (D), (E) and (F). Refer to Illustration 3. Tighten the bolts to a torque of 115 N·m (85 lb ft). Rotate the wheel by two complete revolutions.

6. Repeat Step 5 two more times.

7. Use a depth micrometer to measure the distance between the outside face of the retainer and the end of the spindle. Measure the distance through the two holes which are directly opposite each other. Average the two dimensions and record the average as dimension (C) .

   Note: In addition to the hole pattern in the retainer plate, there are two holes in the retainer plate which can be used to measure dimension (C) .

   Note: If the two measurements differ by more than 0.13 mm (0.005 inch), restart the adjustment procedure at Step 3. Disassemble the wheel assembly and check for any interferences that would prevent the wheel bearing from seating correctly.

8. Calculate the average gap that is between the end of the spindle and the inside face of the retainer by subtracting dimension (B) from dimension (C). Record the calculation as dimension (X) and remove retainer (4) .

9. Calculate the thickness of the shim pack (3). Add 0.254 mm (0.0100 inch) to the calculated dimension (X) .

10. Install the correct thickness of shim pack (3), that was calculated in Step 9, between the end of the spindle and the retainer.

    Note: Caterpillar does NOT recommend installing the screen assembly.

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NOTICE
After the bolts have been torque turned once, DO NOT RE-USE the bolts.

11. Use the following items to install the retainer (4) : fifteen NEW bolts (5), three bolts (5) that were used in Step 5 and eighteen washers (6). Tighten the bolts in a cross pattern to a torque of 250 ± 25 N·m (184 ± 18 lb ft).

12. Tighten the bolts in a cross pattern to a torque of 500 ± 50 N·m (369 ± 37 lb ft).

13. Repeat Step 12 until there is no movement in the bolt.

14. When the proper torque has been reached, tighten the bolts in a cross pattern to an additional 60 ± 5 degrees.

The high capacity bearings for the rear wheel consist of the following parts: 212-5030 Bearing Cone and 175-3770 Cup. Refer to the Service Information System for the latest list of wheels that use the high capacity bearings. These wheels are only on the 793C Off-Highway Trucks.

The high capacity bearings were effective with 793C (S/N: 4AR80).

Note: The former parts in the following list can be reworked in order to accept the high capacity bearings for the wheel: 8X-0252 Final Drive, Brake and Wheel, 107-3152 Final Drive, Brake and Wheel, 113-4328 Final Drive, Brake and Wheel, 125-6508 Final Drive, Brake and Wheel, 0R-3818 Final Drive, Brake and Wheel and 0R-8287 Final Drive, Brake and Wheel .

Note: The new 162-0755 Retainer is available as a direct replacement for the former 106-6542 Retainer. The former 106-6542 Retainer can be reworked to the 162-0755 Retainer dimensions. For the rework procedure, see Service Magazine, SEPD0453, 25 January 1999, "Improved Final Drive Wheel Bearing Retainer Plate Available for Certain Off-Highway Trucks".

The new vertical wheel bearing adjustment procedure is effective with the following items: 793C (S/N: 4GZ145), 0R-9046 Final Drive, Brake and Wheel and 0R-9049 Final Drive, Brake and Wheel (S/N 17193).

Vertical Wheel Bearing Adjustment Procedure For Cast Wheels And Fabricated Wheels Of The 789, 789B And 789C Off-Highway Trucks

Illustration 4	g00659584
This is a cross section view of a wheel group assembly. (A) Tapped hole (1) Cup (2) Cone (3) Shim Pack (4) Retainer (5) Bolts (6) Washers

Illustration 5	g00659589
Area (C) The gap is determined by the dimension (C) minus the dimension (B) .

Illustration 6	g00675311
View (B-B) Sequence for the initial tightening procedure (D) Bolt (E) Bolt (F) Bolt (G) Bolt (H) Bolt (4) Retainer

Use the following procedure to adjust the wheel bearings.

1. Clean the tapped holes (A) in the end of the spindle in order to receive the bolts for the retainer (4) .

2. Use an outside micrometer to measure the thickness of the retainer (4). Measure the thickness near the bolt holes in three different locations. Average the three dimensions and record the average as dimension (B). Refer to Illustration 5.

3. Ensure that the following parts are installed correctly: Cup (1), Cone (2) and reaction hub. Use five NEW bolts (5) in order to install the retainer (4) on the spindle. Install the five NEW bolts into holes that are equally spaced. Refer to Illustration 4 and Illustration 6.

4. Release the brakes.

   Note: The oil pressure that is required to release the brakes is approximately 4685 ± 200 kPa (680 ± 29 psi).

5. Tighten the five NEW bolts (5) in a clockwise bolt tightening sequence: (D), (E), (F), (G) and (H). Refer to Illustration 6. Tighten the bolts to a torque of 100 N·m (74 lb ft). Rotate the wheel by two complete revolutions.

6. Repeat Step 5 two more times.

7. Use a depth micrometer to measure the distance between the outside face of the retainer and the end of the spindle. Measure the distance through the two holes which are directly opposite each other. Average the two dimensions and record the average as dimension (C) .

   Note: In addition to the hole pattern in the retainer plate, there are two holes in the retainer plate which can be used to measure dimension (C) .

   Note: If the two measurements differ by more than 0.13 mm (0.005 inch), restart the adjustment procedure at Step 3. Disassemble the wheel assembly and check for any interferences that would prevent the wheel bearing from seating correctly.

8. Calculate the average gap that is between the end of the spindle and the inside face of the retainer by subtracting dimension (B) from dimension (C). Record the calculation as dimension (X) and remove the retainer (4) .

9. Calculate the thickness of the shim pack (3). Add 0.457 mm (0.0180 inch) to the calculated dimension (X) .

10. Install the correct thickness of shim pack (3), that was calculated in Step 9, between the end of the spindle and the retainer.

    Note: Caterpillar does NOT recommend installing the screen assembly.

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NOTICE
After the bolts have been torque turned once, DO NOT RE-USE the bolts.

11. Use the following items to install the retainer (4) : ten NEW bolts (5), five bolts (5) that were used in Step 5 and fifteen washers (6). Tighten the bolts in a cross pattern to a torque of 400 ± 50 N·m (295 ± 37 lb ft).

12. Repeat Step 11 until there is no movement in the bolts.

13. When the proper torque has been reached, tighten the bolts in a cross pattern to an additional 60 ± 5 degrees.

The new vertical wheel bearing adjustment procedure is effective with the following items: 789C (S/N: 2BW125-UP) and 0R-9043 Final Drive, Brake, and Wheel (S/N 17890).

Vertical Wheel Bearing Adjustment Procedure for Cast Wheels and Fabricated Wheels of the 784B, 784C, 785, 785B and 785C Off-Highway Truck/Tractor

Illustration 7	g00659584
This is a cross section view of a wheel group assembly. (A) Tapped hole (1) Cup (2) Cone (3) Shim Pack (4) Retainer (5) Bolt (6) Washer

Illustration 8	g00659589
Area (C) The gap is determined by the dimension (C) minus the dimension (B) .

Illustration 9	g00675312
View (B-B) Sequence for the initial tightening procedure (D) Bolt (E) Bolt (F) Bolt (G) Bolt (H) Bolt (4) Retainer

Use the following procedure to adjust the wheel bearings.

1. Clean the tapped holes (A) in the end of the spindle in order to receive the bolts for the retainer (4) .

2. Use an outside micrometer to measure the thickness of the retainer (4). Measure the thickness near the bolt holes in three different locations. Average the three dimensions and record the average as dimension (B). Refer to Illustration 8.

3. Ensure that the following parts are installed correctly: Cup (1), Cone (2) and reaction hub. Use five NEW bolts (5) in order to install the retainer (4) on the spindle. Install five NEW bolts into holes that are equally spaced. Refer to Illustration 7 and Illustration 9.

4. Release the brakes.

   Note: The oil pressure that is required to release the brakes is approximately 4685 ± 200 kPa (680 ± 29 psi).

5. Tighten the five NEW bolts (5) in a clockwise bolt tightening sequence: (D), (E), (F), (G) and (H). Refer to Illustration 9. Tighten the bolts to a torque of 80 N·m (59 lb ft). Rotate the wheel by two complete revolutions.

6. Repeat Step 5 two more times.

7. Use a depth micrometer to measure the distance between the outside face of the retainer and the end of the spindle. Measure the distance through the two holes which are directly opposite each other. Average the two dimensions and record the average as dimension (C) .

   Note: In addition to the hole pattern in the retainer plate, there are two holes in the retainer plate which can be used to measure dimension (C) .

   Note: If the two measurements differ by more than 0.13 mm (0.005 inch), restart the adjustment procedure at Step 3. Disassemble the wheel assembly and check for any interferences that would prevent the wheel bearings from seating correctly.

8. Calculate the average gap that is between the end of the spindle and the inside face of the retainer by subtracting dimension (B) from dimension (C). Record the calculation as dimension (X) and remove the retainer (4) .

9. Calculate the thickness of the shim pack (3). Add 0.508 mm (0.0200 inch) to the calculated dimension (X) .

10. Install the correct thickness of shim pack (3), that was calculated in Step 9, between the end of the spindle and the retainer.

    Note: Caterpillar does NOT recommend installing the screen assembly.

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NOTICE
After the bolts have been torque turned once, DO NOT RE-USE the bolts.

11. Use the following items to install the retainer (4) : five NEW bolts (5), five bolts (5) that were used in Step 5 and ten washers (6). Tighten the bolts in a cross pattern to a torque of 250 ± 25 N·m (184 ± 18 lb ft).

12. Repeat Step 11 until there is no movement in the bolts.

13. When the proper torque has been reached, tighten the bolts in a cross pattern to an additional 60 ± 5 degrees.

    Note: The temperature of the final drive oil be decreased by removing the screen assembly and increasing the diameter of the retainer holes. Decreasing the temperature of the final drive oil will increase the life of the wheel bearing. Refer to Service Magazine, SEPD0453, 25 January 1999, "Wheel Station Modifications May Decrease Oil Temperatures on Certain Off-Highway Trucks" for the rework procedure.

The new vertical wheel bearing adjustment procedure is effective with the following items: 785C (S/N: 1HW126-UP) and 0R-9037 Final Drive, Brake and Wheel (S/N 17932).