Notice: In order to prevent overheating of the floor panel or damage to the passenger compartment, insulation, and trim materials, check the underbody for adequate clearance when inspecting or replacing the exhaust system components.

The 4.3L L99 engine, used in the Chevrolet, has a single exhaust system with dual warm-up three-way catalytic converters. The 5.7L LT1 engine, used for both the Chevrolet and the Buick, has a dual exhaust system, with dual warm-up three-way catalytic converters.

The exhaust system does not require periodic maintenance. It is recommended that the condition of the exhaust system be checked if the vehicle is raised for service.

The complete exhaust system, the near by body areas, and the rear compartment lid should be inspected for broken, damaged, missing or mispositioned parts, open seams, holes, loose connections or other deterioration. These conditions could allow exhaust fumes to seep into the rear compartment or into the passenger compartment. Dust or water in the rear compartment may indicate a problem in one of these areas. Any damaged area should be corrected immediately. Whenever installing a new muffler, the resonator, located to the rear of the exhaust muffler, should be replaced also.

Caution: Prolonged operation of a misfiring or flooded engine may cause the catalytic converter to overheat. Damage to the catalyst, the operating vehicle, or personal injury may result.

The dual catalytic converter system, is also known as the warm-up three-way catalytic converter system. Warm-up three-way catalytic converters, which are added to the exhaust system, are emission control devices that reduce the amount of pollutants from the exhaust gas stream.

Notice: In order to avoid damage to the catalyst, use unleaded fuel only.

The catalysts' coatings contain platinum and rhodium. The three-way catalyst lowers the levels of nitrogen oxides (NO3), hydrocarbons (HC) and carbon monoxide (CO).

The exhaust muffler has a tri-flow design. The exhaust muffler has a slot in the outlet pipe that indexes a key (tab), welded on the exhaust resonator inlet, to help maintain alignment.

Important: The installation of exhaust system supports is very important, as improperly installed supports can cause vibrations, which are difficult to diagnose.

Two types of hangers are used in the exhaust system. The first type of hanger uses a rigid metal brace that attaches to the transmission housing, and solidly bolts to both, the right and left sides of the exhaust system. Vibration dampeners attach to both sides of the exhaust system. Catalytic converter cracking may occur if the brace and the dampeners are not installed.

The second type of hanger utilizes a pair of molded rubber insulators, which are pierced by four metal rods. Two of the rods connect from the exhaust system component supported by the hanger. These rods pierce the lower holes of the insulators. The remaining two rods, piercing the upper holes of the insulators, connect to the chassis-mounted hanger bracket.

Caution: Exhaust may enter the vehicle and cause personal injury if the slip joints are not coated with exhaust system sealer before assembly.

Three methods are used for connecting exhaust system components: Slip joints with U-bolt-type clamps, bolt and cup fittings and flange-to-flange fittings.

Before attaching the exhaust system components together, all of the mating surfaces must be clean and in good condition. Flange-to Flange fittings are the only fittings that require gaskets.

The resonator allows the usage of mufflers with less back pressure, and it provides for the best exhaust system-tuning characteristics. Dual exhaust systems utilize two resonators, single exhaust systems utilize one resonator. The resonators and tailpipes are serviced as an assembly.

Servicing the exhaust system includes the following items: