On 6.0l and 8.1l engines, raising and supporting the vehicle first, then, using transmission jack, supporting the transmission is necessary to replace the Catalytic Converter. Strip the transmission mount transmission support nuts and lift up the transmission off the support and remove the transmission support crossmember bolts and crossmember. After that, detach the
Muffler, disconnect the connector position assurance (CPA) retainers and the
Oxygen Sensor electrical connectors (1, 2). Loosen the right exhaust manifold pipe nuts and remove the left exhaust manifold pipe nuts. Loosen the transmission slightly by using the transmission jack and pull out the Catalytic Converter, shifting its hanger out of the
Exhaust Pipe hanger bracket. If your vehicle is equipped with a 6.0l engine and can be ordered with its regular production option (RPO) y91, then remove the Catalytic Converter again and slide the hanger out. When replacing the Catalytic Converter, apply anti-seize compound gm p/n 12377953 or equivalent to the threads of old oxygen sensors and install them, making a total torque of 42 nm (31 ft. Lbs.). For a 6.0l with rpo y91, install a new exhaust seal to exhaust manifold then slide the Catalytic Converter hanger into the Exhaust Pipe-hanger bracket. Install one more new exhaust seal to the exhaust manifold, the left one again, then install the left exhaust manifold pipe nuts. Tighten the right exhaust manifold pipe nuts to 50 nm (39 ft. Lbs. ). Raise the transmission a bit with the use of the jack, connect the Oxygen Sensor electrical connectors (1, 2) as well as the cpa retainers. Reinstall the Muffler, the transmission support crossmember and its bolts, tightening to 95 nm(70 ft. Lbs.). Lower the transmission onto the support, install transmission mount on the transmission support nuts and tighten them to 40 nm (30 ft lbs.). Finally, take the support off of the transmission and lower the vehicle.