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HOMESERVICE MANUALSCHEVROLET1977FORWARD CONTROL 7.4L ENG VIN Y, AUTOMATIC TRANS, TRANS MFR CD 400/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE MECHANICALAUXILIARY EMISSION CONTROL SYSTEMSCATALYTIC CONVERTERSSERVICECATALYST (BEAD) REPLACEMENTAMERICAN MOTORS & GENERAL MOTORS
1977 Chevrolet Forward Control 7.4L Eng VIN Y, Automatic Trans, Trans Mfr CD 400/M40

American Motors & General Motors

1977 Chevrolet Forward Control 7.4L Eng VIN Y, Automatic Trans, Trans Mfr CD 400/M40SECTION American Motors & General Motors
  1. Raise vehicle and attach Vacuum Aspirator Device (J-25077) to exhaust pipe. See Fig 1.
  2. Apply enough air pressure (minimum 60 psi) to hold catalyst beads in place while converter fill plug is removed.
  3. Clamp on vibrator and catalyst receptacle. See Fig 2. Disconnect air supply from vacuum aspirator and attach it to vibrator unit.
  4. Using similar air pressure, vibrator should operate to empty the converter of the catalytic beads in about 10 minutes.
    Fig 1: Vacuum Aspirator Installation
    G09327159Courtesy of NOT AVAILABLE
  5. When all catalyst material is removed, disconnect air supply and remove container from converter and discard beads.
  6. Fill container with approved replacement catalyst beads and install a fill tube fixture to the vibrator device.
  7. Attach air supply to both vibrator and aspirator. With container attached to fill tube, catalyst beads will begin to move into converter.
  8. When catalyst beads stops flowing, disconnect air supply to vibrator and note level of catalyst. It should be even with fill plug. Add more catalyst beads if required.
  9. Apply nickle-base, anti-seize compound to fill plug. Install plug and tighten to 60 ft. lbs. (81 N.m). If equipped with press-type fill plug, install "bridge-and-bolt" type service plug and torque to 28 ft. lbs. (38 N.m).
Fig 2: Placement of Vibrator & Catalyst Container
G09327160Courtesy of NOT AVAILABLE
RENDER: 1.0x

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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.