Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 574 (ENGINE EXHAUST SYSTEM)REPAIR INSTRUCTIONSCATALYTIC CONVERTER REPLACEMENTREMOVAL PROCEDURE

1999 GMC Forward Control 5.7 R, Automatic

Removal Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Removal Procedure

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: To prevent internal damage to the flexible coupling of the catalytic converter assembly, the converter must be supported. The vertical movement at the rear of the catalytic converter assembly must not exceed 6 degrees up or down.

Fig 1: Exhaust Manifold Pipe Stud

Courtesy of GENERAL MOTORS CORP.

Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
If the vehicle is equipped with All-Wheel-Drive, remove the propeller shaft. Refer to Propeller Shaft Replacement in Propeller Shaft.
Remove the catalytic converter nuts from the exhaust manifold studs.
Remove the oxygen sensor. Refer to Heated Oxygen Sensor Replacement - Position 2 in Engine Controls - 3.4L.

Fig 2: View Of Catalytic Converter Bolts

Courtesy of GENERAL MOTORS CORP.

Remove the catalytic converter bolts.
Remove the catalytic converter.

RENDER: 1.0x

NO RELATED

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When to See a Mechanic

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.