Frame flex
- Thread starter x MadMAX DIESEL
- Start date
I found a problem with gm rear 2 mounts causing what they call frame beaming. The fix is the replace those with the updated mounts. Idk what beaming is? Side to side movement or the flex I am seeing??
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I was just gonna call dealer and have them figure it out. But I think I'm gonna get poly ones instead if they will be stiffer than rubber
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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)""
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.
http://www.gmpartsdirect.com/
GM PART # 25791031
CATEGORY: All
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $38.78
OUR PRICE: $23.80
GM PART # 25791032
CATEGORY: All
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $38.78
OUR PRICE: $23.80
GM PART # 15854745
CATEGORY: All
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $3.47
OUR PRICE: $2.13
GM Campaign #PIT3009J
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beaming is NOT causing the "problem" you are having with the frame bending. The beaming is a harmonics driven vibration. The updated mounts just mask it better, not fix it. Your problem is just physics. You put a stress point at a weaker part of the frame and then pulled down on the opposite end really really hard with the sled. Same exact thing as using a long as cheater bar to break a bolt loose. Except you're just torquing on the frame with your breaker bar (aka traction bars/truss in this case), not a bolt.
You closing in that frame will likely fix the frame bending you're having during pulling.
You closing in that frame will likely fix the frame bending you're having during pulling.
I am picking up the lower mount at dealer today. Will see how that does, and will report back. But will box this off season. Too close to end to worry about it right now I think. I think it's gonna help, because it's got a inch travel now before the washer on bolt will stop it. Can't hurt atleast
I'm sure it will help but ain't gunna stop it. If it does, you will be ripping the cab apart soon unless you box it in
Just my opinion here:
The cab and box actually keep the frame from flexing a lot more than people think, good mounts or solid mounts help.
If the frame is going to be trussed it needs to be attached to the vertical part of the frame, the vertical part of the frame is doing the work to keep the frame from bending when a force is applied to the rear of the frame (hitch). If the trussing is attached to the bottom of the frame, the frame should be boxed to make the trussing more effective.
The cab and box actually keep the frame from flexing a lot more than people think, good mounts or solid mounts help.
If the frame is going to be trussed it needs to be attached to the vertical part of the frame, the vertical part of the frame is doing the work to keep the frame from bending when a force is applied to the rear of the frame (hitch). If the trussing is attached to the bottom of the frame, the frame should be boxed to make the trussing more effective.
I don’t know that anyone with would disagree with you about the cab in the box adding rigidity to the frame. That’s proven by the fact that the frame bins in between the cab in the bed. The thing is it’s going to take its toll on the body. Next thing you know you got stress cracks forming doors don’t close like they should etc.
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It bends there mostly because you create a pivot point at the end of your bars or trussing, plus add in what bubba mentioned.
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I wouldn’t count on the body to keep the frame from flexing. If the frame is flexing you need more truss work