GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Savana 🢒 Engine 🢒 Engine Controls - 7.4L 🢒 Catalytic Converter Replacement

Removal Procedure
  1. Raise the vehicle. Support the vehicle with safety stands.

    2. Object Number: 160895 Size: SH
  2. Disconnect the oxygen sensor (O2S) electrical connection.

    3. Object Number: 78428 Size: SH
  3. Remove the nuts and the seals from the exhaust manifold pipes.

    4. Object Number: 363232 Size: SH
  4. On the 4.3L and 5.0L with a 135 inch wheelbase, remove the flange nuts from the front of the muffler.

    5. Object Number: 160928 Size: SH
  5. On the 5.7L and the 7.4L with a 135 inch wheelbase, loosen the clamp from the front of the muffler.

    6. Remove the retaining nuts and gasket from the exhaust flange.


    Object Number: 363245 Size: SH
  6. On the 4.3L and the 5.0L with a 155 inch wheelbase and the 6.5L diesel, remove the flange nuts from the rear of the convertor assembly.

    7. Object Number: 363235 Size: SH
  7. On the 5.7L and the 7.4L with a 155 inch wheelbase, loosen the clamp from the front of the muffler.

    8. Remove the retaining nuts and gasket from the flange.


    Object Number: 363241 Size: SH
  8. On the 5.7L and 7.4L cutaway and RV, remove the retaining nuts and gasket from the exhaust flange at the front of the muffler.

    9. Object Number: 160896 Size: SH
  9. Remove the exhaust hangers as necessary.
  10. Remove the catalytic converter from the vehicle.
  11. Remove the oxygen sensors as necessary.

Installation Procedure
  1. Install the oxygen sensors as necessary.
  2. Apply sealer GM P/N 9985020, or equivalent, to the slip joint connections.
  3. Install the catalytic converter assembly into the front muffler pipe.

    4. Object Number: 160896 Size: SH
  4. Install the exhaust hangers as necessary.

    5. Object Number: 363241 Size: SH
  5. On the 5.7L and the 7.4L cutaway and RV install the new retaining nuts and gasket to the exhaust flange. Do not tighten the flange.

    6. Object Number: 363235 Size: SH
  6. On the 5.7L and 7.4L with a 155 inch wheelbase, install the new retaining nuts and gasket to the exhaust flange.

    7. Do not tighten the flange.

    Do not tighten the clamp.


    Object Number: 160928 Size: SH
  7. On the 5.7L and 7.4L with a 135 inch wheelbase, install the new retaining nuts and gasket to the exhaust flange.

    8. Do not tighten the flange.

    Do not tighten the clamp.


    Object Number: 363245 Size: SH
  8. On the 4.3L and the 5.0L with a 155 inch wheelbase and the 6.5L diesel, install the new retaining nuts and gasket to the rear of the convertor assembly.

    9. Do not tighten the nuts.


    Object Number: 363232 Size: SH
  9. On the 4.3L and 5.0L with a 135 inch wheelbase, install the new retaining nuts and gasket to the front of the muffler.

    10. Do not tighten the nuts.

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.


    Object Number: 78428 Size: SH
  10. Install the new seal and nuts to the exhaust manifold studs.

    11. Tighten

        • Tighten the exhaust manifold nuts to 65 N·m (48 lb ft).
        • Verify that the exhaust system is properly aligned and tighten all the exhaust pipe clamps to 70 N·m (35 lb ft).
        • Tighten the exhaust flange retaining nuts to the muffler to 48 N·m (35 lb ft).

    Object Number: 160895 Size: SH
  11. Connect the oxygen sensor (O2S) electrical connection.
  12. Verify the exhaust system for proper clearance and the alignment of all components.
  13. Remove the safety stands.
  14. Lower the vehicle.