GM 15744826
Front Pipe

In order to change the Catalytic Converter on engines 4.8l and 5.3l, first lift and fix the vehicle, and hook the transmission with an appropriate transmission jack. Remove the transmission mount to transmission support nuts, lift the transmission off the support, and the remove the transmission support crossmember bots and nuts prior to removing the crossmember itself. Next, unclip the engine harness and oxygen sensor pigtail, slacken the cpa retainers, and remove the oxygen sensor electrical connectors. Unclip these connectors from the hose clip and transmission crossmember and remove the left and right exhaust manifold pipe nuts, the exhaust muffler nuts, and the Catalytic Converter lastly. If replacing the Catalytic Converter, apply anti-seize compound gm p/n 12377953, or equivalent, to the threads of the old oxygen sensors and reinstall them, tightening to 42 nm (31 ft. Lbs.). Replace the old Catalytic Converter with a new one and fit new exhaust manifold pipe seals, then tighten the right and left exhaust manifold nuts sixareally then tighten them to 50 nm (39 ft. Lbs.). Introduce the exhaust muffler nuts then tighten them up to 40 nm (30 ft. Lbs.). Reconnect the electrical connectors of oem o2 sensor & cpa retainers, attach the connectors to the hose clip & transmission crossmember & install the clip of engine harness & o2 sensor pigtail. Replace the transmission support cross member and tighten the bolts to 95 nm (70 ft. Lbs.), lower the transmission to the support and install the transmission mount to transmission support nuts tightening both to 40 nm (30 ft. Lbs.). Lastly, take off the transmission jack and lower the vehicle.

The exhaust manifold pipe and seal.

Reinstall the transmission support and lower the vehicle.