Usage:
784B (5RK) Tractors;
785 (8GB),
785B (6HK),
789 (9ZC) 789B (7EK) Trucks
This article supersedes the information for 785 and 789 Trucks given in the Service Magazine; November 5, 1990; Page 7; "New Wheel Bearing Adjustment Procedures". Service Magazine Special Edition; October 30, 1992; Page 204; "New Wheel Bearing Adjustment Procedures". Special Instruction, SENR9306-01, "Procedure To Measure Rear Wheel Bearing End Play".
This procedure applies to setting the wheel bearings in the vertical or horizontal positions, with or without the brake group (parking brake released), and with the Duo-Cone seals installed. This procedure can also be used with the final drive on the machine with the inner tires installed. Make a note of these new methods in the appropriate service manual modules.
Wheel Bearing Adjustment Procedure For The Front Wheels Of 785 Trucks
Illustration 1. Location of components in the 6G-9270 Front Wheel Group on 785 Trucks.
1. Assemble the components of the 6G-9270 Front Wheel Group as shown in Illustration 1. Install retainer (3) with four approximately equally spaced bolts (5). Do not install cover (4).
NOTE: Use only 1B-4367 Bolts (5) (have no lockpatch) when performing the steps to determine the required shim pack thickness. Use new 1B-4367 Bolts (5) for the final assembly.
2. Tighten four bolts (5) to a torque of 200 N·m (150 lb ft).
3. Turn wheel (2) two revolutions.
4. Tighten four bolts (5) again to a torque of 200 N·m (150 lb ft).
5. Completely loosen four bolts (5). Then tighten four bolts (5) to a torque of 80 N·m (60 lb ft).
6. Turn wheel (2) two revolutions.
7. Tighten four bolts (5) again to a torque of 80 N·m (60 lb ft).
8. Turn wheel (2) two revolutions.
9. Continue to repeat Steps 7 and 8 until no further movement of bolts (5) occurs when the specified torque is applied.
10. Use a depth micrometer to measure the distance from the end of axle (1) to the outer face of retainer (3) at the top and bottom of the axle. These measurements are made through the small holes in the retainer. Record the measurements. If there is more than 0.13 mm (.005 in) difference between the two measurements, do not continue with the wheel bearing adjustment. Disassemble and check for any interference that would prevent correct seating of the wheel bearings. Repeat Steps 1 through 9 until the measurements are within 0.13 mm (.005 in). When the measurements are within specification, record the average of the measurements.
11. Remove retainer (3) and measure the thickness of the retainer at the small holes used to make the measurement in Step 10. Use these measurements to determine the average thickness of the retainer.
12. Subtract the average thickness of the retainer from average dimension obtained in Step 10. Record this dimension.
13. Install the shim pack with a thickness equal to the distance measured in Step 12 plus 0.127 mm (.0050 in), between axle (1) and retainer (3).
14. Put 4C-9507 Retaining Compound on the bolt threads before final assembly. Install 14 new 1B-4367 Bolts (5). Tighten bolts (5) to a torque of 250 ± 14 N·m (185 ± 10 lb ft).
Wheel Bearing Adjustment Procedure For The Rear Wheels Of 785 Trucks
Illustration 2. Location of components in the 6G-9345 Rear Wheel Group on 785 Trucks.
1. Install the bearing cups, seal retainer and inner bearing cone on the axle housing (spindle) and place the wheel over the spindle. Make sure the bearing cups are fully seated against the back face of the bore in the wheel.
2. Install the outer bearing cone along with the hub and retainer plate (5) as shown in Illustration 2. Install five clean 1D-4609 Bolts equally spaced around the retainer plate.
3. To seat the bearings, tighten opposite bolts around the bolt circle, to make sure the load application is even, to 200 N·m (150 lb ft).
4. Turn the wheel two complete revolutions and tighten opposite bolts a second time to 200 N·m (150 lb ft).
5. Turn the wheel two complete revolutions and then loosen all bolts 120 degrees (two flats of the bolts head) in opposite sequence. Then tighten the bolts in opposite sequence to 80 N·m (60 lb ft).
6. Rotate the wheel two complete revolutions and tighten the bolts to 80 N·m (60 lb ft).
7. Repeat Step 6 until the bolts do not move when the specified amount of torque is applied.
8. Measure the gap between the retainer plate and the spindle at two opposite holes in the plate. Take the average reading and add 0.178 mm (.0070 in) to determine the thickness of the shim pack to be installed. If there is more than 0.13 mm (.005 in) difference between the two measurements, do not continue with the wheel bearing adjustment. Disassemble and check for any interference that would prevent correct seating of the wheel bearings. Repeat Steps 1 through 9 until the measurements are within 0.13 mm (.005 in). When the measurements are within specification, record the average of the measurements.
9. Slowly and evenly loosen and remove the bolts and retainer plate.
10. Apply 4C-9500 or 6V-1541 Primer and 4C-9507 Retaining compound to the threads of ten new, clean 1D-4609 Bolts. Install the shim pack and bolts. Evenly tighten opposite bolts to 520 N·m (385 lb ft).
Wheel Bearing Adjustment Procedure For The Front Wheels Of 789 Trucks
Illustration 3 Location of components in the 5T-1023 Front Wheel Group on 789 Trucks.
1. Assemble the components of the 5T-1023 Front Wheel Group as shown in Illustration 3. Install retainer (3) with four approzimately equally spaced bolts (5). Do not install cover (4).
NOTE: Use only 1B-4367 Bolts (5) (have no lockpatch) when performing the steps to determine the required shim pack thickness. Use new 1B-4367 Bolts (5) for the final assembly.
2. Tighten four bolts (5) to a torque of 200 N·m (150 lb ft).
3. Turn wheel (2) two revolutions.
4. Tighten four bolts (5) again to a torque of 200 N·m (150 lb ft).
5. Completely loosen four bolts (5). Then tighten four bolts (5) to a torque of 80 N·m (60 lb ft).
6. Turn wheel (2) two revolutions.
7. Tighten four bolts (5) again to a torque of 80 N·m (60 lb ft).
8. Turn wheel (2) two revolutions.
9. Continue to repeat Steps 7 and 8 until no further movement of bolts (5) occurs when the specified torque is applied.
10. Use a depth micrometer to measure the distance from the end of axle (1) to the outer face of retainer (3) at the top and bottom of the axle. These measurements are made through the small holes in the retainer. Record the measurements. If there is more than 0.13 mm (.005 in) difference between the two measurements, do not continue with the wheel bearing adjustment. Disassemble and check for interference that would prevent correct seating of the wheel bearings. Repeat Steps 1 through 9 until the measurements are within 0.13 mm (.005 in). When the measurements are within specification, record the average of the measurements.
11. Remove retainer (3) and measure the thickness of the retainer at the small holes used to make the measurement in Step 10. Use these measurements to determine the average thickness of the retainer.
12. Subtract the average thickness of the retainer from average dimension obtained in Step 10. Record this dimension.
13. Install the shim pack with a thickness equal to the distance measured in Step 12 plus 0.076 mm (.0030 in), between bearing cone (6) and retainer (3).
14. Put 4C-9507 Retaining Compound on the bolt threads before final assembly. Install 14 new 1B-4367 Bolts (5). Tighten bolts (5) to a torque of 250 ± 14 N·m (185 ± 10 lb ft).
Wheel Bearing Adjustment Procedure For The Rear Wheels Of 789 Trucks
Illustration 4. Location of components in the 5T-4476 Rear Wheel Group on 789 Trucks.
1. Install the bearing cups, seal retainer and inner bearing cone on the axle housing (spindle) and place the wheel over the spindle. Make sure the bearing cups are fully seated against the back face of the bore in the wheel.
2. Install the outer bearing cone along with the hub and retainer plate (5) as shown in Illustration 4. Install eight clean 1D-4629 Bolts equally spaced around the retainer plate.
NOTE: Earlier production models may have 1D-4609 Bolts that are 19.0 mm (0.75 in) in diameter.
3. To seat the bearings, tighten opposite bolts around the bolt circle, to make sure the load application is even, to 200 N·m (150 lb ft).
4. Turn the wheel two complete revolutions and tighten opposite bolts a second time to 200 N·m (150 lb ft).
5. Turn the wheel two complete revolutions and then loosen all bolts 120 degrees (two flats of the bolts head) in opposite sequence. Then tighten the bolts in opposite sequence to 95 N·m (70 lb ft).
6. Rotate the wheel two complete revolutions and tighten the bolts to 95 N·m (70 lb ft).
7. Repeat Step 6 until the bolts do not move when the specified amount of torque is applied.
8. Measure the gap between the retainer plate and the spindle at two opposite holes in the plate. If there is more than 0.13 mm (.005 in) difference between the two measurements, do not continue with the wheel bearing adjustment. Disassemble and check for interference that would prevent correct seating of the wheel bearings. Repeat Steps 1 through 9 until the measurements are within 0.13 mm (.005 in). When the measurements are within specification, record the average of the measurements. Take the average reading and add 0.216 mm (.0085 in) to determine the thickness of the shim pack to be installed.
9. Slowly and evenly loosen and remove the bolts and retainer plate.
10. Apply 4C-9500 or 6V-1541 Primer and 4C-9507 Retaining compound to the threads of fifteen new, clean 1D-4629 Bolts. Install the shim pack and bolts. Evenly tighten opposite bolts to 750 N·m (555 lb ft).
NOTE: The earlier machines with 1D-4609 Bolts should be tightened to 520 N·m (385 lb ft).
Measuring Rear Wheel End Play
NOTE: This procedure should be performed at assembly and then again at 2000 hour service intervals and will be used instead of the 2000 hour and 6000 hour wheel bearing adjustments.
This procedure provides a method to measure the rear wheel deflection on the 785, 785B, 789 and 789B Trucks. The deflection can be directly related to the need for wheel bearing adjustment.
A dial indicator with a magnetic base and the ability to raise each axle, individually, are the only tools needed for the deflection measurement.
Rear Wheel Deflection Procedure
1. Stop the truck on a smooth level surface.
2. Place the magnetic base on the inside of the rear brake housing assembly. Position the dial indicator straight down with the tip of the indicator just to the outer edge of the weld bead on the rim assembly. Set the indicator to zero and jack only the axle that the indicator is positioned.
NOTE: Remove any dirt or debris that may interfere with the dial indicator reading.
3. Using blocks and a jack as shown, raise the rear wheels (one side only) off the ground.
4. When the rear wheels are free of the ground, read the indicator and record the total indicator reading (TIR). This is the deflection that will determine what action needs to be taken.
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- * If the TIR is between .000 and .006 no wheel bearing adjustment is necessary.
- * If the TIR is between .007 and .010 the unit should be scheduled for wheel bearing adjustment at the next maintenance interval.
- * If the TIR is over .010 the truck should have the wheel bearings adjusted immediately.
- * If the TIR is between .000 and .006 no wheel bearing adjustment is necessary.
The high TIR indicates an out of adjustment condition or possible wear in the final drive. Use the following wheel bearing adjustment procedure if the deflection indicates adjustment is necessary.