Catalytic Converter: Service and Repair
Removal Procedure1. Raise the vehicle. Support the vehicle with safety stands.
2. Disconnect the Oxygen Sensor (02S) electrical connection.
3. Remove the nuts and the seals from the exhaust manifold pipes.
4. On the 4.3L and 5.0L with a 135 inch wheel base, remove the flange nuts from the front of the muffler.
5. On the 5.7L and the 7.4L with a 135 inch wheel base, loosen the clamp from the front of the muffler.
Remove the retaining nuts and gasket from the exhaust flange.
6. On the 4.3L and the 5.0L with a 155 inch wheel base and the 6.5L diesel, remove the flange nuts from the rear of the convertor assembly.
7. On the 5.7L and the 7.4L with a 155 inch wheel base, loosen the clamp from the front of the muff muffler
Remove the retaining nuts and gasket from the flange.
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. 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. Install the exhaust hangers as necessary.
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. On the 5.7L and 7.4L with a 155 inch wheel base, install the new retaining nuts and gasket to the exhaust flange.
Do not tighten the flange.
Do not tighten the clamp.
7. On the 5.7L and 7.4L with a 135 inch wheel base, install the new retaining nuts and gasket to the exhaust flange.
Do not tighten the flange.
Do not tighten the clamp.
8. On the 4.3L and the 5.0L with a 155 inch wheel base and the 6.5L diesel, install the new retaining nuts and gasket to the rear of the convertor assembly.
Do not tighten the nuts.
9. On the 4.3L and 5.0L with a 135 inch wheel base, install the new retaining nuts and gasket to the front of the muffler.
Do not tighten the nuts.
Notice: Refer to Fastener Notice in Service Precautions.
10. Install the new seal and nuts to the exhaust manifold studs.
^ Tighten the exhaust manifold nuts to 65 Nm (48 ft. lbs.).
^ Verify that the exhaust system is properly aligned and tighten all the exhaust pipe clamps to 70 Nm (35 ft. lbs.).
^ Tighten the exhaust flange retaining nuts to the muffler to 48 Nm (35 ft. lbs.).
11. Connect the oxygen sensor (02S) 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.