2004 2500 gmc 4x4 6.6 vibration

[smessler34]

i have a slight hop/vibration at 45 to 50 mph ..ive ruled out tires due to the set of new michelin ltx 245/75/16E i just put on. it also did it previously with the worn tires. i looked for missing "wieghts" on the drive shaft and had the wheels spun without tires to see if the are true and all checks good. just wondering if y'all might have some ideas

thanx for your time
shawn

[christophersond]

What type truck is it? Is it a crew cab, long bed, short bed, etc., single/double drive shaft?

[smessler34]

its a crew cab , short bed 4x4 6.6 w/allison

[christophersond]

I had the same problem with a 2007 GMC Classic long bed, but it was most noticeable while towing my 5th wheel. After much checking/testing it was determined to be a characteristic of the truck, and there was no fix for the problem (TSB # 1844688 applied). With a little proding from the wife, I got rid of the truck by trading it in on my 2009 GMC short bed, with much assistance from the dealership and GM. I haven't experienced the vibration with the short bed truck. I attribute that mostly to the powertrain setup, and the single drive shaft. Both me and the wife are
happy now.:D

[More Power]

Temporarily drop the rear tire air pressure down to a lower level (say 35-psi) to see if it makes a difference. The rear axle is heavy. This represents a lot of unsprung weight that can be set in an oscillating motion at certain speeds, resulting in a low frequency resonant vibration. Changing tire pressure and running new shocks (Bilsteins) might help.

Jim

[cdub0451]

It's called frame beaming. There are a lot of people with this issue. I fixed mine after reading this. You just need two body mounts. It works.

""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.

[More Power]

It's called frame beaming. There are a lot of people with this issue. I fixed mine after reading this. You just need two body mounts. It works......

Thanks for posting the GM campaign info!

Jim

[dually2002]

It's called frame beaming. There are a lot of people with this issue. I fixed mine after reading this. You just need two body mounts. It works.

""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.

Pulled this from the archives.