WickedMom
02-16-2010, 08:42 AM
#PIT3009L: Suspension Vibration Or Frame Beaming At 40-60 MPH (64-80 KM/H) - keywords front rear shake shock spring tire - (Dec 3, 2009)
Subject: Suspension Vibration or Frame Beaming at 40-60 mph (64 - 80 km/h)
Models: 1999-2009 Chevrolet Silverado and Silverado Classic
1999-2009 GMC Sierra and Sierra Classic
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Beam shake vibration is usually felt in the seat and occurring at speeds between 40-50 mph (64 - 80 km/h). Hertz readings using an EVA tool are normally between 8-24 Hz. This condition is most common on extended cab and crew cab models but has also been noted in other models.
Recommendation/Instructions:
The severity of beam shake may vary from vehicle to vehicle. To determine if the concern is beam shake, please perform the following:
•Test drive vehicle to confirm the condition. A beam shake condition will usually respond to concrete type pavements more than asphalt, so the vehicle should be driven over both surfaces if possible.
•Place 200-500 pounds in the pickup bed between the closed tailgate and the wheel wells. A beaming condition should dissipate.
Note: Tires with excessive Radial Force Variation (RFV) or out-of-roundness can intensify the frame beaming concern. The following radial force variation numbers should be used as a guide:
P-Metric tires (2wd 1500)
12 lbs or less
P-Metric tires (all others)
24 lbs or less
LT-tires
30 lbs or less
If the concern is determined to be beam shake, this is a characteristic of the vehicle. GM Engineering has released updated body mounts to reducing this concern for the Crew and Extended Cab Models. There will be no changes made to the Regular Cab Models.
FOR CREW AND EXTENDED CAB MODELS, REPLACE THE REAR CAB MOUNTS WITH UPDATED PARTS LISTED BELOW. THESE PARTS SHOULD NOT BE USED ON REGULAR CAB MODELS.
Note: 2009 1500 MODELS (WITHOUT RPO Z83) ALREADY HAVE THESE NEW BODY MOUNTS. DO NOT REPLACE THE BODY MOUNTS ON THESE VEHICLES FOR THIS ISSUE.
New upper and lower mounts should be installed at the left and right rear cab position. The new LOWER mount is a two piece design, meaning there is a rubber mount with a metal washer. Some models may use a one piece lower mount, meaning the rubber mount has a metal washer molded into it. If the vehicle has the one piece lower mount design, washers (PN 15854745, Qty 2) will be needed to be used with the new lower mount.
Note: Some new body mounts may have an oily film covering them. This oily film may be left on the mounts during the assembly process and does not indicate a faulty mount. Do not replace the mount for this issue.
Upper Mount 25791031 Qty 2 (DO NOT USE ON 2009 1500 MODELS WITHOUT RPO Z83, see note above)
Lower Mount 25791032 Qty 2 (DO NOT USE ON 2009 1500 MODELS WITHOUT RPO Z83, see note above)
Washer 15854745 Qty 2 (if needed)
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.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
Subject: Suspension Vibration or Frame Beaming at 40-60 mph (64 - 80 km/h)
Models: 1999-2009 Chevrolet Silverado and Silverado Classic
1999-2009 GMC Sierra and Sierra Classic
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Beam shake vibration is usually felt in the seat and occurring at speeds between 40-50 mph (64 - 80 km/h). Hertz readings using an EVA tool are normally between 8-24 Hz. This condition is most common on extended cab and crew cab models but has also been noted in other models.
Recommendation/Instructions:
The severity of beam shake may vary from vehicle to vehicle. To determine if the concern is beam shake, please perform the following:
•Test drive vehicle to confirm the condition. A beam shake condition will usually respond to concrete type pavements more than asphalt, so the vehicle should be driven over both surfaces if possible.
•Place 200-500 pounds in the pickup bed between the closed tailgate and the wheel wells. A beaming condition should dissipate.
Note: Tires with excessive Radial Force Variation (RFV) or out-of-roundness can intensify the frame beaming concern. The following radial force variation numbers should be used as a guide:
P-Metric tires (2wd 1500)
12 lbs or less
P-Metric tires (all others)
24 lbs or less
LT-tires
30 lbs or less
If the concern is determined to be beam shake, this is a characteristic of the vehicle. GM Engineering has released updated body mounts to reducing this concern for the Crew and Extended Cab Models. There will be no changes made to the Regular Cab Models.
FOR CREW AND EXTENDED CAB MODELS, REPLACE THE REAR CAB MOUNTS WITH UPDATED PARTS LISTED BELOW. THESE PARTS SHOULD NOT BE USED ON REGULAR CAB MODELS.
Note: 2009 1500 MODELS (WITHOUT RPO Z83) ALREADY HAVE THESE NEW BODY MOUNTS. DO NOT REPLACE THE BODY MOUNTS ON THESE VEHICLES FOR THIS ISSUE.
New upper and lower mounts should be installed at the left and right rear cab position. The new LOWER mount is a two piece design, meaning there is a rubber mount with a metal washer. Some models may use a one piece lower mount, meaning the rubber mount has a metal washer molded into it. If the vehicle has the one piece lower mount design, washers (PN 15854745, Qty 2) will be needed to be used with the new lower mount.
Note: Some new body mounts may have an oily film covering them. This oily film may be left on the mounts during the assembly process and does not indicate a faulty mount. Do not replace the mount for this issue.
Upper Mount 25791031 Qty 2 (DO NOT USE ON 2009 1500 MODELS WITHOUT RPO Z83, see note above)
Lower Mount 25791032 Qty 2 (DO NOT USE ON 2009 1500 MODELS WITHOUT RPO Z83, see note above)
Washer 15854745 Qty 2 (if needed)
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.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION