Installation Procedure

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Refer to EXHAUST SYSTEM INSPECTION NOTICE in Cautions and Notices.

NOTE: Refer to FASTENER NOTICE in Cautions and Notices.

If the catalytic converter was replaced, perform the following:
1. 1.1. Apply anti-seize compound GM P/N 12377953 or equivalent to the threads of the old oxygen sensors.
2. 1.2. Install the oxygen sensors.
Tighten

Tighten the sensors to 42 N.m (31 lb ft).

Fig 1: Installing Oxygen Sensors (6.0L & 8.1L)
Courtesy of GENERAL MOTORS CORP.
If equipped with a 6.0L engine, with RPO Y91, install a NEW exhaust seal to the exhaust manifold.
Install the catalytic converter.
Slide the catalytic converter hanger into the exhaust pipe hanger bracket.

Fig 2: Installing Catalytic Converter (6.0L w/RPO Y91)
Courtesy of GENERAL MOTORS CORP.
Install a NEW exhaust seal to the exhaust manifold.
Install the catalytic converter.
Slide the catalytic converter hanger into the exhaust pipe hanger bracket.

Fig 3: Installing Catalytic Converter (6.0L & 8.1L)
Courtesy of GENERAL MOTORS CORP.
Install the left exhaust manifold pipe nuts.
Tighten the right exhaust manifold pipe nuts.
Tighten

Tighten the nuts to 50 N.m (39 lb ft).
Using the transmission jack, raise the transmission slightly.

Fig 4: Installing Left Exhaust Manifold Pipe Nuts (6.0L & 8.1L)
Courtesy of GENERAL MOTORS CORP.
Connect the oxygen sensor electrical connectors (1, 2).
Connect the CPA retainers.
Install the muffler. Refer to Muffler Replacement (4.3L, 4.8L, and 5.3L Engines) or Muffler Replacement (6.0L, 6.6L, and 8.1L Engines) .

Fig 5: Connecting Oxygen Sensor Electrical Connectors (6.0L & 8.1L)
Courtesy of GENERAL MOTORS CORP.
Install the transmission support crossmember.
Install the transmission support crossmember bolts.
Tighten

Tighten the bolts to 95 N.m (70 lb ft).

Fig 6: Installing Transmission Support Crossmember & Bolts (6.0L & 8.1L)
Courtesy of GENERAL MOTORS CORP.
Lower the transmission onto the transmission support.
Install the transmission mount to transmission support nuts.
Tighten

Tighten the nuts to 40 N.m (30 lb ft).
Remove the support from the transmission.
Lower the vehicle.

Fig 7: Installing Transmission Mount To Transmission Support Nuts (6.0L & 8.1L)
Courtesy of GENERAL MOTORS CORP.