Exhaust Boom/Groan Noise in Passenger Compartment (Install Exhaust Bracket and Dampers to Exhaust System)

Some customers may comment on a low frequency noise heard in the passenger compartment with the vehicle in "Drive" and at or near idle. The noise is often described as pressure in the ears.

The noise may be due to the exhaust system "exciting" and causing the disturbing frequency.

Follow the service procedure below to correct this condition.

Raise the vehicle. Refer to Lifting and Jacking the Vehicle in the Service Manual (SI Document ID #6771).

Bracket Installation Procedure for 1997-1999 Vehicles

1. Remove the two bolts and two nuts from the transmission mount.
2. Support the transmission with a suitable adjustable jack stand.
3. Raise the rear of the transmission with the adjustable jack stand.



4. Remove the two lower exhaust flange nuts (3) located on the flange in front of the converter.
5. Remove the two bolts (4) securing the transmission mount (1) to the extension housing.
6. Remove the two nuts securing the transmission mount (1) to the crossmember.
7. Reposition the transmission mount (1) in order to allow access for the installation of the bracket (P/N 15172526) (2) inside of the transmission mount (1) and onto the two lower exhaust flange studs (3).
8. Position the transmission mount (3) into the correct location. Lower and remove the adjustable jack stand from under the vehicle.
9. Reinstall the two lower nuts and two upper bolts (4) onto the transmission mount (1).
10. Reinstall the two lower exhaust flange nuts (3).

Tighten

1. Tighten the two transmission mount bolts to 50 N·m (37 lb ft).
2. Tighten the two transmission mount nuts to 57 N·m (42 lb ft).
3. Tighten the two exhaust flange nuts to 35 N·m (26 lb ft).

Bracket Installation Procedure for 2000-2002 Vehicles

1. Remove the two bolts (4) securing the transmission mount (1) to the extension housing.
2. Install the bracket (P/N 15172527) (3) by sliding the bracket into the transmission mount (1).
3. Reinstall the two transmission mount bolts (4) and hand tighten at this time.
4. Install the exhaust clamp (P/N 15595206) (2) onto the exhaust pipe.

Tighten

•	Tighten the two transmission mounting bolts to 25 N·m (18 lb ft).

•	Tighten the two clamp nuts to 30 N·m (22 lb ft).

Damper Installation Procedure (All Vehicles)

Important: When installing the exhaust dampers, it is critical to maintain at least 25.4 mm (1 in) clearance from all other components.

1. Install the damper (P/N 10281828) (1) using clamp (P/N 15595206) (3) 60 mm (2.4 in) rearward of the muffler (2) and as parallel to the ground as possible.

Tighten
Tighten the two clamp nuts to 30 N·m (22 lb ft).





Important: When installing the exhaust dampers, it is critical to maintain at least 25.4 mm (1 in) clearance from all other components.

2. Locate the far most exhaust hanger (1) on the tail pipe (3).
3. Install the second exhaust damper (P/N 10281828) (2) using clamp (P/N 15595206) (3) 60 mm (2.4 in) rearward of the exhaust hanger (1) and 315 mm (12.4 in) in front of the tail pipe end (3) and as parallel to the ground as possible.

Tighten
Tighten the two clamp nuts to 30 N·m (22 lb ft).

4. Lower the vehicle.

Parts are expected to be available 5-1-2002 from GMSPO.

For vehicles repaired under warranty, use: