Catalytic Converter for GMC C/K Trucks (1996-1999) 5.7L

Direct-Fit Catalytic Converter Assembly for 1996-1999 GMC C/K Trucks (GMT400)

What it Does: The catalytic converter assembly replaces degraded or blocked factory converters on 1996-1999 GMC C/K Trucks to restore proper exhaust scavenging, eliminate excessive backpressure, and resolve emissions trouble codes.

The Stock GMC C/K Trucks Substrate Degradation

With decades of operational heat cycles, the factory emissions hardware on GMT400 trucks routinely suffers from fractured ceramic washcoats, core melting, and carbon fouling caused by high-mileage oil blow-by or rich air-fuel mixtures. Over time, physical substrate breakdown restricts flow inside the dual-inlet collector pipe, driving up exhaust gas temperatures (EGTs), choking the top-end volumetric efficiency of the Vortec 5700 L31 engine, and triggering persistent P0420/P0430 catalyst efficiency DTC faults.

The Engineering Solution

This direct-replacement exhaust assembly is manufactured from heavy-wall stainless steel tubing coupled to a high-density ceramic honeycomb monolith. Wash-coated with premium noble metal catalysts (platinum, palladium, rhodium), it restores closed-loop stoichiometric conversion efficiency while maintaining smooth, low-restriction laminar exhaust flow. Precision-bent downpipes match factory routing and incorporate pre-welded oxygen sensor ports and thick OE-profile flanges, providing a leak-free bolt-on installation without cut-and-clamp fabrication. Interchangeable with OEM part numbers 645328, 50239, and 50410.

Technical Specifications

Compatibility

• 1996-1999 GMC C1500 5.7L V8
• 1996-1999 GMC K1500 5.7L V8
• Fits 1500 series half-ton models only; does not fit 2500 or 3500 series
• EPA compliant (46-state legal; not legal for sale or use in CA, NY, CO, or ME)

Frequently Asked Questions

Does this fit the GMT400 C/K Trucks?

Yes, this is a direct fit for the 1996-1999 GMC C/K Trucks equipped with the Vortec 5.7L L31 engine.

Will installing this unit resolve active catalyst efficiency check engine lights?

Yes, assuming oxygen sensors and upstream engine management are operating within factory tolerances, this unit restores standard emissions efficiency to clear P0420 and P0430 fault codes.

The GMC Heavy-Duty Durability Standard

Constructed to endure demanding payload hauling and high-load towing cycles, this heavy-duty stainless assembly resists road salt corrosion, extreme thermal shock, and frame-twist vibration encountered on rugged job sites.