Backlash Adjustment 8.6 Inch Axle

Tools Required

1. Install the J 25025-1 and the J 8001 to the axle housing as shown.
2. Place the indicator stem of the J 8001-3 at the heel end of a gear tooth.
3. Set the J 8001-3 so that the stem is aligned with the gear rotation and perpendicular to the tooth angle.
4. Preload the dial of the J 8001-3 .

Align the needle and the dial face of the J 8001-3 to ZERO.

5. While holding the drive pinion stationary, move the ring gear back and forth.

Measure and record the backlash.

6. Repeat the measuring procedure at eight points around the ring gear.

Specification
The difference between the backlash at all of the measuring points should not vary by more than 0.05 mm (0.002 in).

7. If the difference between the backlash at all of the measuring points varies by more than 0.05 mm (0.002 in), inspect for the following conditions:

•

Burrs

•	A distorted case flange

•	Uneven bolting

8. If the difference between all the measuring points is within specifications, the backlash at the minimum lash point measured should be:

Specification
The backlash between the ring gear and the drive pinion should be between 0.08-0.25 mm (0.003-0.010 in) with a preferred backlash of 0.13-0.18 mm (0.005-0.007 in).

Important: 

•	Do not use the original cast iron production shims to adjust the backlash. Use service shims and spacers instead.

•	Adjust the thickness of the shim pack on each side of the differential in equal amounts. This will maintain the correct axle side bearing preload.

•	Moving 0.05 mm (0.002 in) of shim thickness from one side of the differential to the other will change the backlash adjustment approximately 0.03 mm (0.001 in).

9. If the backlash is too small, increase the backlash using the following procedure:

9.1.	Remove the bearing cap bolts and the bearing caps.

Mark the bearing caps left or right.

9.2.	Remove the differential case assembly with the bearing cups and the shims.

Mark the bearing cups and the shims left or right.

9.3.	Measure the thickness of left side shim pack.

Measure the production shim or the shim and service spacer in 3 locations.

Measure each shim separately.

9.4.	Calculate the average of the 3 measurements for each shim.

Add the average of each of the shim measurements together.

Record the measurement. This is the thickness for the left side shim pack.

9.5.

Assemble a new left side shim pack by decreasing the appropriate amount of thickness from the original left side shim pack. If the original shim is cast iron production shim, assemble the shim pack using a service spacer and service shims. For example, to increase the backlash by 0.05 mm (0.002 in), remove 0.10 mm (0.004 in) of thickness from the left side shim pack.

9.6.	Measure the thickness of right side shim pack.

Measure the shim or the shim and service spacer in 3 locations.

Measure each shim separately.

9.7.	Calculate the average of the 3 measurements for each shim.

Add the average of each of the shim measurements together.

Record the measurement. This is the thickness for the right side shim pack.

9.8.

Assemble a new right side shim pack by increasing the appropriate amount of thickness to the original right side shim pack. If the original shim is cast iron production shim, assemble the shim pack using a service spacer and service shims. For example, to increase the backlash by 0.05 mm (0.002 in), add 0.10 mm (0.004 in) of thickness to the right side shim pack.

10. If the backlash is too large, decrease the backlash using the following procedure:

10.1.

Remove the bearing cap bolts and the bearing caps.

Mark the bearing caps left or right.

10.2.

Remove the differential case assembly with the bearing cups and the shims.

Mark the bearing cups and the shims left or right.

10.3.

Measure the thickness of left side shim pack.

Measure the production shim or the shim and service spacer in 3 locations.

Measure each shim separately.

10.4.

Calculate the average of the 3 measurements for each shim.

Add the average of each of the shim measurements together.

Record the measurement. This is the thickness for the left side shim pack.

10.5.

Assemble a new left side shim pack by increasing the appropriate amount of thickness to the original left side shim pack. If the original shim is cast iron production shim, assemble the shim pack using a service spacer and service shims. For example, to increase the backlash by 0.05 mm (0.002 in), add 0.10 mm (0.004 in) of thickness to the left side shim pack.

10.6.

Measure the thickness of right side shim pack.

Measure the shim or the shim and service spacer in 3 locations.

Measure each shim separately.

10.7.

Calculate the average of the 3 measurements for each shim.

Add the average of each of the shim measurements together.

Record the measurement. This is the thickness for the right side shim pack.

10.8.

Assemble a new right side shim pack by decreasing the appropriate amount of thickness to the original right side shim pack. If the original shim is cast iron production shim, assemble the shim pack using a service spacer and service shims. For example, to decrease the backlash by 0.05 mm (0.002 in), remove 0.10 mm (0.004 in) of thickness to the right side shim pack.

11. Install the differential case assembly with the bearing cups.
12. Install the left side service spacer between the axle housing and the differential case.
13. Install the right side service spacer between the axle housing and the differential case.



14. Install the left side service shim using the J 25588 , if necessary.

The service shim must be installed between the service spacer and the differential bearing cup.

15. Install the right side service shim using the J 25588 , if necessary.

The service shim must be installed between the service spacer and the differential bearing cup.

Notice: Refer to Fastener Notice in the Preface section.

16. Install the bearing caps and bolts.

Tighten
Tighten the bolts to 75 N·m (55 lb ft).

17. Recheck the backlash and adjust, if necessary.
18. Once backlash is correct, perform a gear tooth contact pattern check in order to ensure proper alignment between the ring and pinion gears. Refer to Gear Tooth Contact Pattern Inspection .

Backlash Adjustment 9.5 Inch LD Axle

Tools Required

Important: 

1. Measure the rotating torque of the drive pinion and differential assembly using an inch-pound torque wrench.

Specification
The rotating torque of the drive pinion and differential assembly should be 3.4-6.2 N·m (30-55 lb in) for new bearings or 2.8-5.1 N·m (25-45 lb in) for used bearings.

2. If the rotating torque is too low, tighten the differential bearing adjuster nut in one slot increments until the specified rotating torque is obtained.
3. If the rotating torque is too high, loosen the differential bearing adjuster nut in one slot increments until the specified rotating torque is obtained.
4. If the specification for the rotating torque of the drive pinion and differential assembly cannot be obtained by adjusting the differential bearing adjuster nut, remove the differential assembly, measure the rotating torque of the drive pinion and adjust as necessary. Refer to Differential Replacement and Drive Pinion Bearings Replacement .



5. Install the J 25025-1 and the J 8001-3 to the axle housing as shown.
6. Place the indicator stem of the J 8001-3 at the heel end of a gear tooth.
7. Set the J 8001-3 so that the stem is aligned with the gear rotation and perpendicular to the tooth angle.
8. Preload the dial of the J 8001-3 approximately ¾ of a turn.

Align the needle and the dial face of the J 8001-3 to ZERO.

9. While holding the drive pinion stationary, move the ring gear back and forth.

Measure and record the backlash.

10. Repeat the measuring procedure at eight points around the ring gear.

Specification
The difference between the backlash at all of the measuring points should not vary by more than 0.05 mm (0.002 in).

11. If the difference between the backlash at all of the measuring points varies by more than 0.05 mm (0.002 in), inspect for the following conditions:

•

Burrs

•	A distorted case flange

•	Uneven bolting

12. If the difference between all the measuring points is within specifications, the backlash at the minimum lash point measured should be:

Specification
The backlash between the ring gear and the drive pinion should be between 0.08-0.25 mm (0.003-0.010 in) with a preferred backlash of 0.13-0.18 mm (0.005-0.007 in).

Important: Increasing or decreasing the shim thickness by 0.05 mm (0.002 in) will change the backlash adjustment approximately 0.03 mm (0.001 in).

13. If the backlash is not within specifications, adjust the backlash by performing the following procedure:

13.1.

Remove the differential bearing adjuster nut retainer bolt.

13.2.

Remove the differential bearing adjuster nut retainer.

13.3.

Loosen the bearing cap bolts.

Do not remove the bearing cap bolts.

13.4.

Loosen the differential bearing adjuster nut using the J 24429 .

13.5.

Remove the differential side bearing shim.

13.6.

Measure the thickness of the shim.

Measure the shim in 3 locations.

13.7.

Calculate the average of the 3 measurements.

Record the measurement.

13.8.

If the backlash is too small, select a smaller shim than the one that was removed. For example, to increase the backlash by 0.05 mm (0.002 in), select a shim that is 0.10 mm (0.004 in) thinner than the shim that was removed.

13.9.

If the backlash is too large, select a larger shim than the one that was removed. For example, to increase the backlash by 0.05 mm (0.002 in), select a shim that is 0.10 mm (0.004 in) thicker than the shim that was removed.

13.10.

Install the shim.

14. Tighten the differential bearing adjuster nut using the J 24429 until the differential bearing adjuster nut is seated against the bearing cup .
15. Once the differential bearing adjuster is seated against the differential bearing, tighten the differential bearing adjuster nut using the J 24429 the following additional amounts:

Tighten

•	For used bearings, tighten the differential bearing adjuster nut an additional 2 slots.

•	For new bearings, tighten the differential bearing adjuster nut an additional 3 slots.

16. Tighten the differential bearing cap bolts.

Tighten
Tighten the bearing cap bolts to 85 N·m (63 lb ft).

17. Recheck the backlash following the steps above to verify that the backlash is within specifications.
18. Install the differential bearing adjuster nut retainer.
19. Install the differential bearing adjuster nut retainer bolt.

Tighten
Tighten the differential bearing adjuster nut retainer nut bolt to 26 N·m (19 lb ft).

20. Measure the drive pinion and differential case side bearing preload and adjust, if necessary following the steps above.
21. Once the backlash and bearing preload is correct, perform a gear tooth contact pattern check in order to ensure proper alignment between the ring and pinion gears. Refer to Gear Tooth Contact Pattern Inspection .