Exhaust Muffler Replacement 4.8L and 5.3L Engines
                    Tools Required
J 38185  Hose Clamp
Pliers
Removal Procedure
- Remove the rear tires
and wheels. Refer to 
Tire and Wheel Removal and Installation 
 in Tires and  Wheels.
 
- Remove the oil pan skid plate bolts and plate, if necessary. 
 
- Remove the spare tire.
 
- If servicing a vehicle
equipped with regular production option (RPO) Z55, disconnect the chassis
 harness from the following electrical connectors:
 
| •  | Electronic suspension rear position sensor (1) | 
 
Important: Do not attempt to pry the rear suspension sensor link rod from the rear
position sensor ball stud.
- Remove the left and right sensor link rods from the sensors, perform
the following:
 
| 5.1.  | Support the sensor lever with your hand | 
 
| 5.2.  | Twist the link rod in order to remove it from the ball stud | 
 
- Install adjustable jack stands under the rear axle.
 
- Remove the rear axle vent
hose from the rear axle, if necessary.
 
- Remove the vent hose swivel clip from the rear brake crossover
pipe.
 
- Remove the rear shock
absorbers lower bolts and nuts. 
 
- Lower the rear axle slightly, using the adjustable jack stands,
in order to remove the muffler. 
 
- Remove the exhaust muffler
nuts.
 
- Remove the muffler from
the insulators.
 
Installation Procedure
- Apply lubricant to the
exhaust insulators in order to aid in installation.
 
- Install the muffler to the insulators.
 
Notice: Use the correct fastener in the correct location. Replacement fasteners
must be the correct part number for that application. Fasteners requiring
replacement or fasteners requiring the use of thread locking compound or sealant
are identified in the service procedure. Do not use paints, lubricants, or
corrosion inhibitors on fasteners or fastener joint surfaces unless specified.
These coatings affect fastener torque and joint clamping force and may damage
the fastener. Use the correct tightening sequence and specifications when
installing fasteners in order to avoid damage to parts and systems.
- Install the exhaust muffler nuts.
 
Tighten
Tighten the nuts to 40 N·m (30 lb ft).
- Raise the rear axle, using
the adjustable jackstands.
 
- Install the lower bolts and nuts to the rear shock absorbers.
 
Tighten
Tighten the rear bolts to 95 N·m (70 lb ft).
- Remove the adjustable jack stands from under the rear axle.
 
- Install the vent hose
swivel clip to the rear brake crossover pipe.
 
- Install the rear axle vent hose to the rear axle, if necessary.
 
- If servicing a vehicle,
equipped with RPO Z55, install the left and right sensor link rods to the
 sensors. Using J 38185 
install  the link rods to the ball studs on the sensor levers.
 
- Connect the chassis harness to the following electrical connectors:
 
| •  | Electronic suspension rear position sensor (1) | 
 
- Install the spare tire. 
 
- Install the oil pan skid
plate and bolts, if necessary. 
 
Tighten
Tighten the bolts to 20 N·m (15 lb ft).
- Install the rear tires and wheels. Refer to 
Tire and Wheel Removal and Installation 
 in Tires and Wheels.
 
                            Exhaust Muffler Replacement 6.0L and 8.1L Engines
                    Tools Required
J 38185  Hose Clamp
 Pliers
Removal Procedure
- Remove the rear tires
 and wheels. Refer to 
Tire and Wheel Removal and Installation 
 in Tires and  Wheels.
 
- Remove the oil pan skid plate bolts and plate, if necessary. 
 
- Remove the spare tire. 
 
- If servicing a vehicle
 with regular production option (RPO) Z55, disconnect the chassis harness
from   the following electrical connectors:
 
| •  | Electronic suspension rear position sensor (1) | 
 
Important: Do not attempt to pry the rear suspension sensor link rods from the
 rear position sensor ball studs.
- Remove the left and right sensor link rods from the sensors, perform
 the following:
 
| 5.1.  | Support the sensor lever with your hand | 
 
| 5.2.  | Twist the link rod in order to remove it from the ball stud | 
 
- Install adjustable jack stands under the rear axle.
 
- If equipped with a 8.6
 or 9.5 inch ring gear, remove the rear axle vent hose from the rear axle,
  if necessary.
 
- Remove the vent hose swivel clip from the rear brake crossover
 pipe.
 
- If equipped with a 10.5
 inch ring gear, remove the rear axle vent hose from the rear axle, if necessary.
 
- Remove the vent hose swivel clip from the rear brake crossover
 pipe.
 
- Remove the rear shock
 absorbers lower bolts and nuts. 
 
- Lower the rear axle slightly, using the adjustable jack stands,
 in order to remove the muffler. 
 
- Unclip the oxygen sensor
 connector from the frame.
 
- Disconnect the connector position assurance (CPA) retainer.
 
- Disconnect the oxygen sensor electrical connector.
 
- Unclip the oxygen sensor
 connector from the support.
 
- Disconnect the CPA retainer.
 
- Disconnect the oxygen sensor electrical connector.
 
- Unclip the oxygen sensor
 connector from the support.
 
- Disconnect the CPA retainer.
 
- Disconnect the oxygen sensor electrical connector.
 
- If equipped with a 6.0L
 engine, perform the following:
 
| •  | Unclip the oxygen sensor connector from the frame. | 
 
| •  | Disconnect the CPA retainer. | 
 
| •  | Disconnect the oxygen sensor electrical connector. | 
 
- Remove the exhaust muffler
 nuts.
 
- Loosen the exhaust pipe clamp.
 
- With the aid of an assistant, support the exhaust muffler.
 
- Remove the insulators
 from the frame hangers.
 
- With the aid of an assistant, slide the muffler rearward in order
 to remove the muffler from the catalytic converter.
 
- Remove the insulators from the muffler hangers.
 
- Remove the exhaust manifold pipe gasket.
 
- Remove the oxygen sensor
 if the muffler is being replaced.
 
Installation Procedure
- If the muffler was replaced
 reinstall the old oxygen sensor.
 
- Apply anti-seize compound GM P/N 12377953 or equivalent
 to the threads of the old oxygen sensor.
 
Notice: Use the correct fastener in the correct location. Replacement fasteners
must be the correct part number for that application. Fasteners requiring
replacement or fasteners requiring the use of thread locking compound or sealant
are identified in the service procedure. Do not use paints, lubricants, or
corrosion inhibitors on fasteners or fastener joint surfaces unless specified.
These coatings affect fastener torque and joint clamping force and may damage
the fastener. Use the correct tightening sequence and specifications when
installing fasteners in order to avoid damage to parts and systems.
- Install the oxygen sensor.
 
Tighten
Tighten the oxygen sensor to 42 N·m (31 lb ft).
Important: Apply lubricant to the insulators to aid in installation.
- Install the insulators to the muffler hangers.
 
- Install a new exhaust manifold pipe gasket.
 
- With the aid of an assistant, slide the muffler forward in order
 to install the muffler to the catalytic converter.
 
- Install the insulators to the frame hangers.
 
- Install the exhaust muffler
 nuts, until snug.
 
- Tighten the exhaust pipe clamp bolt and muffler nuts.
 
Tighten
|     •  | Tighten the exhaust muffler nuts to 40 N·m (30 lb ft). | 
 
|     •  | Tighten the exhaust pipe clamp to 40 N·m (30 lb ft). | 
 
- If equipped with a 6.0L
 engine, perform the following:
 
| •  | Connect the oxygen sensor electrical connector. | 
 
| •  | Connect the CPA retainer. | 
 
| •  | Clip the oxygen sensor connector to the frame. | 
 
- Connect the oxygen sensor
 electrical connector.
 
- Connect the CPA retainer.
 
- Clip the oxygen sensor connector to the support.
 
- Connect the oxygen sensor
 electrical connector.
 
- Connect the CPA retainer.
 
- Clip the oxygen sensor connector to the support.
 
- Connect the oxygen sensor
 electrical connector.
 
- Connect the CPA retainer.
 
- Clip the oxygen sensor connector to the frame.
 
- Raise the rear axle using
 the adjustable jack stands. 
 
- Install the rear shock absorbers lower bolts and nuts. 
 
Tighten
Tighten the lower bolts to 95 N·m (70 lb ft).
- Remove the adjustable jack stands from under the rear axle.
 
- If equipped with a 10.5
 inch ring gear, connect the vent hose swivel clip to the rear brake crossover
  pipe.
 
- Install the rear axle vent hose to the rear axle, if necessary.
 
- If equipped with a 8.6
 or 9.5 inch ring gear, connect the vent hose swivel clip to the rear brake
  crossover pipe.
 
- Install the rear axle vent hose to the rear axle, if necessary.
 
- If servicing a vehicle
 equipped with RPO Z55, install the left and right sensor link rods to the
  sensors. Using J 38185 
install
  the link rods to the ball studs on the sensor levers.
 
- Connect the chassis harness to the following electrical connectors:
 
| •  | Electronic suspension rear position sensor (1) | 
 
- Install the spare tire.
 
- Install the oil pan skid
 plate and bolts, if necessary. 
 
Tighten
Tighten the bolts to 20 N·m (15 lb ft).
- Install the rear tires and wheels. Refer to 
Tire and Wheel Removal and Installation 
 in Tires and Wheels.