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Home >> Chevrolet >> 1990 >> Step Van 7.4 N, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 14 (Drive Axle - 7.5", 7.625", 8.5" & 9.5") >> Overhaul >> Reassembly & Adjustments >> Side Bearing Preload (7 1/2", 7 5/8" & 8 1/2" Ring Gear)

Side Bearing Preload (7 1/2", 7 5/8" & 8 1/2" Ring Gear)

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  1. Side bearing preload is adjusted by varying the thickness of both left and right side bearing shims equally. Lubricate bearings and place differential assembly into position in housing. Hold in place by hand.
  2. Install Bearing Strap (J-22779-6) on left bearing. Tighten bolts evenly to a snug fit. Install right bearing cap. Tighten bolts to a snug fit.
  3. Position ring gear tight against pinion so backlash is .000-.001" (0-.025 mm). Insert Gauge (J-22779) between left bearing cup and carrier housing.
  4. While moving gauge up and down, tighten adjusting nut on end of gauge until a slight drag is felt. Tighten lock bolt on side of tool.
  5. Install adjustment spacer and shim between right bearing cup and axle housing. Determine bearing preload by inserting progressively larger feeler gauges between carrier and shim. The point just before drag begins is the correct feeler gauge thickness. This is the zero setting without preload.
  6. Remove bearing strap, gauge, spacer, shim, feeler gauge and differential case from axle housing. Using a micrometer, measure and average readings in 3 places on gauge. Record measurement.
  7. Add together dimensions of shim, spacer and feeler gauge. Subtract .010" (.25 mm) from ring gear (left) side measurement and add .010" (.25 mm) to opposite (right) side measurement. This allows for correct backlash adjustment.
  8. To obtain correct preload, add .004" (10 mm) to both measurements. The total is correct shim pack thickness for each side.
    • Ring Gear Side (Left) Shim Pack
    • .250" (Gauging Tool Measurement)
    • -.010" (Backlash Adjustment)
    • +.004" (Bearing Preload)
    • =.244" (Ring Gear Side Shim Pack)
    • Opposite Ring Gear Side (Right) Shim Pack
    • .265" (Combined Measurement Total)
    • +.010" (Backlash Adjustment)
    • +.004" (Bearing Preload)
    • =.279" (Opposite Ring Gear Side Shim Pack)
  9. Install ring gear side shim first. Wedge opposite side shim between bearing cup and spacer. Install shim so chamfered side is against spacer.
    NOTE: If shim is not chamfered enough and scrapes spacer when it is installed, file or grind chamfer before installation.
  10. It may be necessary to partially remove differential when right side shim is installed. Tap shim into place with a soft-faced hammer. Tighten bearing cap bolts to specifications. Check backlash. See BACKLASH & FINAL ASSEMBLY  in this article.
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