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Home >> GMC >> 1991 >> Magnavan 5.7 K >> Repair and Diagnosis >> Suspension >> Rear Suspension >> Suspension - Rear - G Series >> Trouble Shooting >> Shock Absorbers >> Spiral Groove

Spiral Groove

  1. Remove shock absorber. See SHOCK ABSORBER  under REMOVAL & INSTALLATION.
  2. Purge the air from the pressure chamber. Extend the shock vertically, top end up. Turn the shock over and collapse it vertically, top end down. Repeat the above step 5 times.
  3. Place the shock absorber in a vise with the jaws clamped onto the shock's bottom mount. Shock absorber should be positioned vertically in the vise, top end up. Do not clamp the vise jaws on the shock's reservoir tube.
  4. Pump the shock absorber at various rates of speed and observe the, rebound force. Rebound force is normally stronger than the compression force (approximately 2-to-1). Rebound force should be smooth and constant for each stroke rate.
  5. Compare with a good shock absorber.
  6. If one of the following conditions are observed, replace the shock absorber. See SHOCK ABSORBER  under REMOVAL & INSTALLATION.
    • A skip or lag at reversal near mid-stroke.
    • A seize (except at the extreme ends of travel).
    • A noise (grunt or squeal) after completing one full stroke in both directions.
    • A clicking noise at fast reversal.
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