Catalytic Converter: Service and Repair

Removal Procedure





1. Raise and suitably support the vehicle with safety stands. Refer to Vehicle Lifting.
2. Remove the transmission rear support. Refer to Transmission Support Replacement.
3. Disconnect the oxygen sensor (02S) electrical connection.





4. Remove the nuts and the seals from the exhaust manifold pipes.





5. On the 4.3L and 5.0L with a 135 inch wheelbase, remove the flange nuts from the front of the muffler.





6. Perform the following steps on the 5.7L and the 7.4L with a 135 inch wheelbase.
^ Loosen the clamp from the front of the muffler.
^ Remove the retaining nuts and gasket from the exhaust flange.





7. 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.





8. Perform the following steps on the 5.7L and the 7.4L with a 155 inch wheelbase.
^ Loosen the clamp from the front of the muffler.
^ Remove the retaining nuts and gasket from the flange.





9. 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.





10. Remove the exhaust hangers as necessary.
11. Remove the catalytic converter from the vehicle.
12. 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 wheelbase, 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 wheelbase, 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 wheelbase 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 wheelbase, 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 the exhaust pipe flange to exhaust manifold studs.
^ Tighten the exhaust pipe flange to 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 (52 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. Install the transmission support. Refer to Transmission Support Replacement.
13. Verify the exhaust system for proper clearance and the alignment of all components.
14. Remove the safety stands and lower the vehicle. Refer to Vehicle Lifting.