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

This PI was superseded to update model years and combine PI's. Please discard PIT3222B.

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 2002-2008 regular wheelbase, coil spring mid-sized utilities (Envoy and Trailblazer) only built prior to 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 worse on coil spring equipped vehicles 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.

On coil spring equipped vehicles, if the resonance/boom noise has improved but not completely eliminated with installation of new design rear coil springs, 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 planed for this concern.

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

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.