Rush/Buzz/Hiss Type Noise Heard in Passenger Compartment (Add Foam Tape to Underbody Fuel Lines)

Some customers may comment on a rush/buzz/hiss type noise that can be heard in the passenger compartment. This noise is most apparent when the vehicle is in the Drive position at idle.

The cause of this condition may be due to the underbody fuel lines making contact with the body in the area above the transmission bellhousing.

Add foam tape to the underbody at the area of contact using the procedure listed below.

1. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in the General Information sub-section of the Service Manual.
2. Remove the right side assist step front bracket.

2.1.	Remove the two nuts and the U-bolt securing the step to the front mounting bracket.

2.2.	Remove the two nuts securing the front bracket to the frame.

2.3.	Loosen the remaining bracket to frame nuts to allow the front bracket to be removed.

3. Install the transmission jack to the transmission and support the transmission.
4. Remove the transmission support.

4.1.	Disconnect the transmission wiring harness from the support.

4.2.	Remove the transmission mount to the transmission support stud nuts.

4.3.	Remove the transmission support to the frame nuts and bolts.

4.4.	Remove the transmission support from the vehicle.

5. Remove the front propeller shaft.
6. Lower the transmission in order to gain access to the top of the transmission.
7. On the underbody, locate the contact point. A visual witness mark should be seen.
8. Use an isopropyl alcohol based solution to clean the vehicle body surface.
9. Add two sealer patches, P/N 88987942, to the underbody.
10. Raise the transmission into position.
11. Install the front propeller shaft.
12. Install the transmission support.

12.1.

Install the transmission support into the vehicle.

12.2.

Install the transmission support to the frame nuts and bolts.

Tighten:
Tighten the nuts to 54 N·m (40 lb ft).

12.3.

Install the transmission mount to the transmission support stud nuts.

Tighten:
Tighten the nuts to 57 N·m (42 lb ft).

12.4.

Connect the transmission wiring harness to the support.

13. Remove the transmission jack.
14. Install the right side assist step front bracket.

14.1.

Install the front bracket and tighten the remaining bracket to frame nuts.

Tighten:
Tighten the nuts to 35 N·m (26 lb ft).

14.2.

Install the two nuts securing the front bracket to the frame.

Tighten:
Tighten the nuts to 35 N·m (26 lb ft).

14.3.

Install the two nuts and the U-bolt securing the step to the front mounting bracket.

Tighten:
Tighten the nuts to 20 N·m (15 lb ft).

15. Lower the vehicle.

*Only available in box of 25. Use 2 per vehicle and return any unused material to dealer stock for future use.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: