Suspension Vibration or Frame Beaming at 40-60 mph (64-80 km/h) - keywords front rear shake shock spring tire

This PI was superceded to add additional fix information. Please discard PIT3009G.

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

Some customers may comment on a vibration which is usually felt in the seat and typically occurs at speeds between 40-60 mph (64 - 80 km/h). Hertz readings using an EVA tool are normally between 8-24 Hz. This condition is most common in extended cab and crew cab models but has also been noted in other models and is typically referred to as Beam Shake.

The severity of beam shake may vary from vehicle to vehicle. To determine if the concern is beam shake, please perform the following:

1. 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.
2. 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 should be considered a normal characteristic of the vehicle, however, GM Engineering has released updated body mounts to help minimize this concern for the light duty 1500 Crew and Extended Cab Models Only. There will be no changes made to the regular cab 1500, 1500HD, 2500 or 3500 models.

FOR LIGHT DUTY 1500 CREW AND EXTENDED CAB MODELS, REPLACE THE REAR CAB MOUNTS WITH UPDATED PARTS LISTED BELOW. THESE PARTS SHOULD NOT BE USED ON REGULAR CAB 1500, 1500HD, 2500 or 3500 MODELS.

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) must be used with the new lower mount.

Upper Mount 25791031 Qty 2

Lower Mount 25791032 Qty 2

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.