Boom / Rumbling Noise At Highway Speed - keywords body frame int intermittent moan rear resonance spring suspension TCC vibration

This PI was superseded to update Condition/Concern. Please discard PIT3222C.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Bulletin # 02-03-09-002C was released to address 2002-2005 regular wheelbase, coil spring mid-sized utilities (Bravada, Envoy and Trailblazer) only built prior to August 23, 2004. After performing the bulletin, a vehicle may have some remaining level of the resonance/boom noise concern described in TSB # 02-03-09-002C. With the new springs installed, the concern is typically described as being improved but not eliminated.

Vehicles equipped with optional rear air suspension RPO G67 (Bravada, Rainier, Envoy XL, Envoy XUV, Envoy and some Saab 97x models) and/or extended wheel base (Envoy XL, Envoy XUV and Trailblazer EXT) are NOT addressed in TSB # 02-03-09-002B. Although this concern may be experienced in all midsized utilities, the noise is generally more audible on coil spring equipped regular wheel base vehicles. Extended wheel base and/or air suspension equipped vehicles experience noise levels that are within an acceptable range and no repairs are recommended.

Note: The rear coil springs referenced in Bulletin # 02-03-09-002C are manufactured with an updated coating. These springs were placed into production on August 23, 2004. Do not perform this bulletin for vehicles built after August 23, 2004.

On ALL coil spring equipped vehicles listed above with the new coated type coil springs installed, it should be explained to the customer that this noise is a characteristic of the vehicle and further repairs should not be attempted.

For G67 equipped vehicles, This concern is a normal operating characteristic of the vehicle. It will be important to compare the noise of a troubled vehicle to a known good vehicle with the same engine, suspension and body style. No future repairs are planned for this concern.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.