GM 15798957
Muffler

To change Muffler on 6.0l, 6.6l and 8.1l engines, first lift and support the vehicle, including remove spare tire if necessary, and under the rear axle install adjustable jacks if necessary. In the case of an 8.6 or 9.5 inch ring gear, plug the rear axle vent hose and swivel clip from rear brake crossover pipe, and when it comes to the vehicle with a ring gear of 10.5 inch follow the same steps. If necessary, remove the lower bolts and nuts of the rear shock absorbers, and then relieve the rear axle by lowering it using the adjustable jack stands. For 6.0l or 8.1l, remove nuts of the exhaust Muffler nuts and loosen the Exhaust Pipe clamp while carefully holding the Muffler exhaust to prevent it from falling down on the jobsite. For the 6.6l engine, also remove nuts from the exhaust Muffler and support the Muffler. Remove the insulators in the frame hangers for 6.0l or 8.1l engines, slide the Muffler rearward out of the Catalytic Converter, and then take off the insulators from Muffler hangers. If needed, peel off the exhaust manifold pipe gasket and for the 6.6l engine, take out the insulators from the frame hangers while sliding the Muffler towards the rear to separate it from the exhaust Muffler pipe. Pull off the exhaust Muffler gasket if necessary, and for 6.0l or 8.1l engines, pull out the Oxygen Sensor if the Muffler itself is being replaced. If the band clamp is not being replaced along with the Muffler, then the band clamp needs to be replaced, marking its position on the intermediate Exhaust Pipe, grinding and weld to remove the weld, and install a new band clamp. In case of installation that had the Muffler changed on 6.0l or an 8.1l engine, the old Oxygen Sensor needs to be re-installed with anti-seize compound gm p/n 12377953 on its threads, which were to be tightened to 42 nm (31 ft. Lbs. ). For the 6.6l engine, attach insulator to Muffler hangers and lubricate it to make it easier to install. Replace the exhaust Muffler gasket with a new one, then slide the Muffler forward to attach it to the exhaust Muffler pipe, before fitting insulators to frame hanger. For 6.0l or 8.1l engine, install the insulators to the Muffler hangers, lubricating them as well. Replace the exhaust manifold pipe gasket and slide the Muffler to the front connecting it to the Catalytic Converter and replace its riding to the frame hangers. For the 6.6l engine, the nuts for the exhaust Muffler must be tightened to 40 nm (30 ft. Lbs.). For 6.0l and 8.1l engines, set the new band clamp on the intermediate Exhaust Pipe next to the old one marked with a band clamp bolt, where tightening the exhaust Muffler nuts is meant to be done in such a way that the band clamp bolt installed in such a way that it would not be placed below the Exhaust Pipe itself. Secure the Exhaust Pipe clamp bolt to 44 nm (33 ft lbs). If required, raise the rear axle with adjustable jack stands, install the rear shock absorbers lower, bolts and nuts inserting them into place as tight as it gets 95 nm (70 ft. Lbs.). For 10.5 inch ring gear vehicles, install the rear axle vent hose and attach the vent hose swivel clip to the rear brake crossover pipe. For those with an 8.6 or 9.5 inch ring gear, fit the rear axle vent hose in and hook up vent hose swivel clip. Finally, take off the adjustable jack stands and install the spare tire if must and also lower down the vehicle.

The first step to replacing a Muffler on a 2500/3500 cab/chassis vehicle with 6.0l engine requires you to lift the vehicle for support and eliminate the spare tire if it exists. The installation of adjustable jack stands under the rear axle must be done before removing the rear axle vent hose and swivel clip from the rear brake crossover pipe if the vehicle has an 8.6 or 9.5 inch ring gear. Referring to vehicles with 10.5 inch ring gear rings, follow the procedures for the vent hose installation process. You need to start by taking out the rear Shock Absorber lower bolts and nuts before using the adjustable jack stands to lower the rear axle. You need to start by removing the exhaust Muffler to exhaust manifold pipe nuts and relaxing the exhaust Muffler clamp before pulling out the heated Oxygen Sensor (HO2S). A helper can assist in removing the insulators (1-4) from their positions on the front, intermediate, and rear Muffler assembly hangers after you apply lubrication to the 4 insulator areas. To install the parts, reapply lubrication to the 4 insulators then position the Muffler assembly with assistance before reinstalling the insulators (1-4). Tighten the exhaust Muffler clamp to 47 n.m (35 lb ft) after reinstalling the ho2s while installing the exhaust Muffler to exhaust manifold pipe nuts which should be tightened to 45 n.m (33 lb ft). Lift the rear axle through adjustable jack stands while reinstalling the rear Shock Absorber lower bolts and nuts securely to 95 n.m (70 lb ft). First install the rear axle vent hose and then position its swivel clip to the rear brake crossover pipe when you have a 10.5 inch ring gear. The rear axle vent hose and the vent hose swivel clip installation requires a 8.6 or 9.5 inch ring gear. If needed, replace the spare tire before taking down the vehicle by removing the adjustable jack stands.

Position the exhaust pipe with a NEW gasket to the turbocharger, ensuring the tab on the gasket faces inward, and loosely install the bolts.

Install a new exhaust manifold pipe seal to the exhaust manifold pipe before installing the pipe itself.

Raise and support the vehicle, removing the spare tire if needed, and install adjustable jack stands under the rear axle.

Remove the exhaust muffler nuts, loosen the exhaust pipe clamp, and support the exhaust muffler with assistance.

First, raise and support the vehicle appropriately.

Remove the heated oxygen sensor (HO2S) and support the transmission with a suitable transmission jack.