GM 15296921
Muffler

Wear protective goggles and gloves when replacing the Muffler systems on vehicles powered by 4.3l, 4.8l, 5.3l, or 6.0l engines and observe exhaust service security protocols. Muffler replacements happen as one complete system with Exhaust Pipe and Tail Pipe with aftermarket tail pipes existing in some vehicles. Start the procedure by lifting the frame which lowers the rear axle position. You need to disconnect the nuts from the Catalytic Converter pipe flange on a 4.3l-single-pipe setup to access it. For 4.8l, 5.3l or 6.0l engines utilizing dual Catalytic Converter pipes, start by loosening the right clamp and unfastening the left Catalytic Converter nuts at the Muffler flange. Two people might be needed to remove exhaust hanger insulator pins because of their weight unless the vehicle's wheelbase matches the exhaust system's length precisely. Manually lift the Muffler assembly above the rear axle before removing it in the direction of the vehicle front. During installation you need two people to position the Muffler assembly from the front of the vehicle and lift it over the rear axle. Fasten the Muffler assembly hanger pins to the exhaust hanger insulators. To install the retaining nuts and new gasket on the front of the Muffler you need to properly tighten the Catalytic Converter to Muffler retaining nuts using 48 n.m (35 lb ft). Right catalytic converters for 4.8l 4.3l and 6.0l engines need to be installed within the Muffler followed by a clamp nut torque to 54 n.m (40 lb ft). When installing the left Catalytic Converter to the Muffler flange use a new gasket while tightening the retaining nuts to 48 n.m (35 lb ft) to achieve proper exhaust system alignment; proceed by tightening the right Catalytic Converter clamp to 54 n.m (40 lb ft) and the left Catalytic Converter to Muffler flange nuts also to 48 n.m (35 lb ft). Finally, lower the vehicle.

Before replacing the Muffler, make sure goggles and gloves are worn, and keep in mind exhaust service precautions. The Muffler is serviced as a unit with an Exhaust Pipe and a Tail Pipe and if the aftermarket Tail Pipe is involved it may modify the process. Increase the height of the vehicle by the frame to decrease the rear axle. Remove the nuts holding the Catalytic Converter pipe off of the Muffler flange from a vehicle equipped with a single Catalytic Converter pipe that has a 4.3 l engine. For a 4.8/5.3/6.0l engine with dual Catalytic Converter pipes, loosen the clamp for the right Catalytic Converter pipes and remove the nuts that hold the left Catalytic Converter to the Muffler flange. While the wheelbase of the vehicle, and size and length of the vehicle's exhaust system, disconnect the Muffler assembly hanger pins from exhaust hanger insulators. It is also may require at least two personnel because of the weight of the exhaust system. Pull the Muffler assembly over the rear axle and remove it towards the front end of the car. In the case of installation, raise the Muffler assembly above the rear axle, from the front of the vehicle, and possibly with use; two individuals can raise it, install the hanger pins of the exhaust hanger insulators. If optional 4.3l engine, install the retaining nuts and new gasket to the front of Muffler and tightening the Catalytic Converter to Muffler retaining nuts, 48 nm (35 ft. Lbs). For 4.8/4.3l/6.0l engine, put right Catalytic Converter in Muffler and tighten the clamp nut to 54 nm (40 ft lbs). Replace the new gasket and the nuts screwing the left Catalytic Converter to the Muffler flage, make sure the exhaust system is aligning correctly and tighten the right Catalytic Converter clamp to 54nm (40ft. Lbs.) and the Catalytic Converter to Muffler flage nuts to 48 n (35ft. Lbs.). Finally, lower the vehicle.

Before beginning Muffler replacement for vehicles with 4.3l, 4.8l, 5.3l or 6.0l engines drivers must protect their eyes with goggles while wearing gloves and follow exhaust service protocols. All Muffler components including Exhaust Pipe and Tail Pipe form one servicing unit while aftermarket Tail Pipe replacements could exist in some vehicles. The frame of the vehicle needs to be raised to lower the rear axle position. A 4.3l engine with one Catalytic Converter pipe requires removal of all Muffler flange retaining nuts for the converter pipe. To service the left Catalytic Converter pipes on 4.8l/5.3l/6.0l engine vehicles loose the right clamp then use a wrench to remove all the nuts from the left converter's connection to the Muffler flange. The procedure for removing the exhaust hanger pins from exhaust hanger insulators must be performed by two people since the weights involved can exceed individual capability. Transfer the Muffler assembly over the rear axle while pulling it forward so that the front of the vehicle becomes reachable. Two people might be needed to lift the Muffler assembly from the front of the vehicle over the rear axle before installing hanger pins onto exhaust hanger insulators. When working on the front of the Muffler with a 4.3l engine you need to install retaining nuts and a new gasket afterward then torque the Catalytic Converter to Muffler retaining nuts to 48 n.m (35 lb.ft). 4.8l/4.3l/6.0l engine owners should place the right Catalytic Converter into the Muffler and use a torque wrench to tighten the clamp nut to 54 n.m (40 lb ft). Insert the left Catalytic Converter assembly while using a new gasket together with the Muffler flange nuts before tightening both the right Catalytic Converter clamp to 54 n.m (40 lb ft) and the left Muffler flange retaining nuts to 48 n.m (35 lb ft). Finally, lower the vehicle.

To replace the Muffler for 6.0l, 6.6l and 8.1l engines, lift and hold the vehicle and remove spare tire if necessary. Put adjustable jack stands under rear axle and if your vehicle comes with an 8.6 inch or 9.5 inch ring gear, remove rear axle vent hose and its swivel clip from the rear brake crossover pipe. Repeat the same process for a 10.5 inch ring gear. Lower the rear axle if necessary by removing the lower bolts and nuts of rear shock absorbers. For 6.0l or 8.1l engines, undo exhaust Muffler nuts and unbolt the Exhaust Pipe clamp. With help, support the exhaust Muffler and unscrew the nuts for the 6.6. Engine. Slide the Muffler rearward to remove it from the Catalytic Converter, taking the insulators off the frame hangers as required. If the Muffler is not to be done as an assembly, position the band clamp of the intermediate Exhaust Pipe, then grind the weld from the band to remove it, and the new band clamp. For installation, when the Muffler was replaced on 6.0l or 8.1l engines, apply the old Oxygen Sensor with the anti-seize compound gm p/n 12377953, tighten to 42 nm (31 ft. Lbs). Apply lubrication to insulators for the easy installation and then mount them on Muffler hangers for 6.6l engines followed by a new exhaust Muffler gasket. Push the Muffler forward to attach it to the Muffler pipe of the exhaust and attach the insulators to the hangers of the frame. Install the insulators on the Muffler hangers and a new exhaust manifold pipe gasket, when you have 6.0l or 8.1l engines. Pull the Muffler forward to attach it to the Catalytic Converter, fit the insulators to the frame hangers, and to the 6.6l engines, install and tighten the Muffler nuts to 40 nm (30 ft.lbs.). Position the new band clamp on the intermediate Exhaust Pipe, so the bolt is not underneath the pipe, installing and tighten the exhaust Muffler nuts as well as the Exhaust Pipe clamp bolt to the specifications of 40 nm (30 ft. Lbs.) and 44 nm (33 ft. Lbs), respectively. Raise the rear axle and install the rear shock absorbers lower bolts and nuts while tightening them up to 95 nm (70 ft. Lbs) and reconnecting the rear axle vent hose and swivel clips if necessary. Finally, take off the adjustable jack stands, replace the spare tire if necessary, and lower the car.

Install the retaining nuts and a new gasket to the front of the muffler, tightening the nuts to 48 Nm (35 lb ft).

Install the nuts for the muffler to the exhaust pipe and the nuts for the catalytic converter pipe to the exhaust pipe, tightening the flange nuts to 48 Nm (35 ft. lbs.).

Loosen the clamp for the right catalytic converter and remove the nuts retaining the left catalytic converter to the muffler flange.