Bouncing at 45-50 MPH

[Todd6.6]

Try searching "frame beaming." Look at the lower body lines between the cab and the front of the bed if they aren't lined-up the the rear body mount is toast!

[Mizfitcreations]

Hmm.... Well after going through the entire front end and everything is tight as it should be, maybe it is the frame beaming. Crazy as the mount doesn't look bad. I did notice a lot of weights were used for these new tires as well....

[GM03HD]

I had the same issue with my truck about two months ago and it was a combination of the ride hight and the tires were not balanced correctly.

[Varty Yo]

Its frame beaming! Try new cab mounts!!!

[Mizfitcreations]

Read through the "frame beaming" page and there was about 6 different part numbers for the new mounts. Anybody have a better number for it? Gmpartsdirect is a hard site to search for stuff. Thanks

[GM03HD]

GM Campaign #PIT3009J: Suspension Vibration Or Frame Beaming At 40-60 MPH (64-80KM/H) - keywords front rear shake shock spring tire - (Sept 18,2008)""


Condition/Concern:

Beam shake vibration is usually felt and occurring at speeds between 40-50 mph (64-80 km/h). Hertz readings using an EVA tool are normally bewtween 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 the 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.

-----------

If the concern is determined to be beam shake, this a characteristic of the vehicle. GM Engineering has released updated body mounts to reduce 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.

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.

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 ccomplete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

[Bransjeep]

Frame beaming for sure


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[Mizfitcreations]

Bransjeep, how do you like the poly bushings? Are they stiffer or still give a good ride? It's gonna cost about the same to get the new rear bushings vs all 6 poly's from what I've seen

[Bustedknuckles]

I had the same exact problem and it was solved by having the tires road force balanced. I had tried several times on our shop balancer and it wouldn't go away. Took it to a place that does roadforce balancing and it rides like a car now!

[Mizfitcreations]

I looked that up and the shop I went to is supposed to have that kind of balancing. I'll have them rebalance and if that doesn't work.... Body mounts