EI07118 - Underbody Noise, Pop, Creak, Body Mount (Engineering Information)

This bulletin is being revised to provide additional diagnostic information under step 6 (in italics). Please discard Corporate Bulletin Number 07-08-61-006 (Section 08 -- Body and Accessories).

Important:  If the customer did not comment about this condition, Do Not proceed with this bulletin.

Some customers may comment on a noise coming from the underbody of the vehicle.

GM Engineering is attempting to determine the root cause of this condition. GM has a need to obtain information about the diagnosis and repair. Use the following procedure to diagnose and repair the vehicle. Note information on the repair order as necessary.

1. Describe the noise (i.e. pop, creak, etc.) and the conditions in which the noise can be duplicated.
2. Remove the bolt-in front crossmember and add washers using the procedure found in Service Bulletin 03-08-61-002H.

•	Re-evaluate the customer's concern.

•	If adding washers to the front crossmember corrected the customers concern, no further repairs are required. Contact engineer Bob Hillier at 248-930-8373 to let him know what corrected the condition.

•	If adding washers to the front crossmember did not correct the customers concern, proceed with step 3.

3. Spray penetrating oil (i.e.: WD-40 or equivalent) on the bushing to the control are area.

•	Re-evaluate the customer's concern.

•	If the noise is eliminated or reduced, replace the control arm assembly. Contact engineer Bob Hillier at 248-930-8373 to let him know what corrected the condition. No further repairs are required - do not proceed with the rest of this bulletin.

•	If the noise was not eliminated or reduced by lubricating the control arm bushing, proceed with step 4.

4. Inspect the ladder shield for any damage. Any damage to the ladder shield may put it in contact with the exhaust system causing a ground out or rattle.

•	If damage to the ladder shield is found, repair the damage and test drive the vehicle to verify the correction. Go to step 7.

•	If no damage is found, go to step 5.

5. Can the noise can be duplicated during low speed turning maneuvers (i.e. parking lot):

•	YES -- complete the following:

-	Remove the front skid plate (H2).

-	Test drive the vehicle to determine if the condition is corrected.

-	If the condition no longer exists with the front skid plate removed, add a washer to shim the front skid plate away from the ladder shield. No further repairs are required. Go to step 7.

-	If the condition still exists with the front skid plate removed, reinstall the front skid plate and go to step 6.

•	NO -- Go to step 6.

6. If it is suspected that the noise is coming from a body mount:

6.1.	Install J 39570 - Chassis Ears to the frame rail at or near the body mounts.

6.2.	Test drive the vehicle to identify which mount is suspect.

6.3.	Measure the torque of the suspect mount(s).

6.4.	Remove the suspect mount. Drive the vehicle and determine if the noise has been eliminated.





6.5.	Inspect the body mount spacer/bracket on the body side. The body mount spacer/bracket on the body side should be flat. Note whether the metal is flat or if the mount appears to be "pulled through" (1). Refer to the above diagram.

6.6.	Do not make any repairs at this time -- Go to step 7.

7. Contact engineer Bob Hillier at 248-930-8373 and provide him with diagnostic information.