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Differential and driveline » 8 1/4 Rear axle » Adjustments
Differential bearing preload and gear backlash

The following must be considered when adjusting bearing preload and gear backlash:

  •  The maximum ring gear backlash variation is 0.003 inch (0.076 mm).

Fig. 55 Gauge Tools In Housing-Typical
Fig. 55 Gauge Tools In Housing-Typical

1 - ARBOR DISC
2 - PINION BLOCK
3 - ARBOR
4 - PINION HEIGHT BLOCK

Fig. 56 Pinion Gear Depth Measurement-Typical
Fig. 56 Pinion Gear Depth Measurement-Typical

1 - ARBOR
2 - SCOOTER BLOCK
3 - DIAL INDICATOR

  • Mark the gears so the same teeth are meshed during all backlash measurements.
  •  Maintain the torque while adjusting the bearing preload and ring gear backlash.
  •  Excessive adjuster torque will introduce a high bearing load and cause premature bearing failure. Insufficient adjuster torque can result in excessive differential case free-play and ring gear noise.
  •  Insufficient adjuster torque will not support the ring gear correctly and can cause excessive differential case free-play and ring gear noise.

NOTE: The differential bearing cups will not always immediately follow the threaded adjusters as they are moved during adjustment. To ensure accurate bearing cup responses to the adjustments:

  •  Maintain the gear teeth engaged (meshed) as marked.
  •  The bearings must be seated by rapidly rotating the pinion gear a half turn back and forth.
  •  Do this five to ten times each time the threaded adjusters are adjusted.

(1) Use Wrench C-4164 to adjust each threaded adjuster inward until the differential bearing freeplay is eliminated (Fig. 57). Allow some ring gear backlash (approximately 0.01 inch/0.25 mm) between the ring and pinion gear. Seat the bearing cups with the procedure described above.

Fig. 57 Threaded Adjuster Tool
Fig. 57 Threaded Adjuster Tool

1 - AXLE TUBE
2 - BACKING PLATE
3 - TOOL C-4164

(2) Install dial indicator and position the plunger against the drive side of a ring gear tooth (Fig. 58).

Measure the backlash at 4 positions (90 degrees apart) around the ring gear. Locate and mark the area of minimum backlash.

(3) Rotate the ring gear to the position of the least backlash. Mark the gear so that all future backlash measurements will be taken with the same gear teeth meshed.

(4) Loosen the right-side, tighten the left-side threaded adjuster. Obtain backlash of 0.003 to 0.004 inch (0.076 to 0.102 mm) with each adjuster tightened to 14 N·m (10 ft. lbs.). Seat the bearing cups with the procedure described above.

(5) Tighten the differential bearing cap bolts 95 N·m (70 ft. lbs.).

(6) Tighten the right-side threaded adjuster to 102 N·m (75 ft. lbs.). Seat the bearing cups with the procedure described above. Continue to tighten the right-side adjuster and seat bearing cups until the torque remains constant at 102 N·m (75 ft. lbs.) (7) Measure the ring gear backlash. The range of backlash is 0.006 to 0.008 inch (0.15 to 0.203 mm).

(8) Continue increasing the torque at the rightside threaded adjuster until the specified backlash is obtained.

Fig. 58 Ring Gear Backlash Measurement
Fig. 58 Ring Gear Backlash Measurement

1 - DIAL INDICATOR
2 - RING GEAR
3 - EXCITER RING

(7) Measure the ring gear backlash. The range of backlash is 0.006 to 0.008 inch (0.15 to 0.203 mm).

(8) Continue increasing the torque at the rightside threaded adjuster until the specified backlash is obtained.

NOTE: The left-side threaded adjuster torque should have approximately 102 N·m (75 ft. lbs.). If the torque is considerably less, the complete adjustment procedure must be repeated.

(9) Tighten the left-side threaded adjuster until 102 N·m (75 ft. lbs.) torque is indicated. Seat the bearing rollers with the procedure described above.

Do this until the torque remains constant.

(10) Install the threaded adjuster locks and tighten the lock screws to 10 N·m (90 in. lbs.).

After the proper backlash is achieved, perform the Gear Contact Analysis procedure.

    More about «Adjustments»:

    1/4 Axle pinion gear depth

    Differential bearing preload and gear backlash

    Gear contact pattern analysis

    Side gear clearance

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