GM 10398370
Muffler

The process requires that you elevate the vehicle before proceeding with Muffler replacement for 6.0l and 8.1l engines. Disconnect the Oxygen Sensor connector and its cpa retainer from the frame then from the support using this procedure multiple times as needed. You must disconnect both the Oxygen Sensor and its sensor connection for the replacement of the 6.0l engine system. Support the Muffler with an assistant while you remove exhaust Muffler nuts and loosen the Exhaust Pipe clamp. The Muffler detachment from the Catalytic Converter can be done by moving it backward while removing insulators from frame hangers and Muffler hangers. When you plan to replace the Muffler you need to take out both the exhaust manifold pipe gasket and the Oxygen Sensor. To replace individual Muffler components, mark the intermediate Exhaust Pipe band clamp position then fully remove the weld before adding a new clamp. The installation of a new Muffler requires a reinstallation of the Oxygen Sensor with anti-seize compound gm p/n 12377953 or equivalent on its threads and a tight torque specification of 42 nm (31 ft. Lbs.). The insulators should receive lubrication before implementment while installers should position them on Muffler hangers with new exhaust manifold pipe gaskets between them. Assistance helps move the Muffler forward until you connect it to the Catalytic Converter before securing the insulators on the frame hangers. Lower the vehicle while placing the new band clamp on the intermediate Exhaust Pipe but keep the bolt positioned above the pipe. Tighten the exhaust Muffler nuts to 40 nm while keeping them about 30 ft. Lbs. Of torque. Secure the clamp by applying torque to 44 nm (33 ft. Lbs.) but not exceeding 40 nm (30 ft. Lbs.) for the nut. Reconnect the Oxygen Sensor electrical connector along with the cpa retainer and secure the connector to the frame and support according to needs.

Place a new exhaust manifold pipe seal onto the exhaust manifold pipe and install the pipe.

Reinstall the exhaust muffler, then the transmission support crossmember and its bolts, tightening them to 95 Nm (70 ft. lbs.).

Remove the transmission support crossmember bolts and the crossmember itself, followed by the exhaust muffler.