Vibration...??

[titanite]

Hello,
Purchased a new 2007 GMC classic duramax. I had the dealership to a 2" lift and went from stock 245 tires to BFG 285R16E's. They reprogrammed tire size with a bully dog triple dog. Picked up the truck and there was a bad vibration in the back end. Took the truck back and they said that the tires were balanced improperly and they had fixed it. So drove it home and although it was better than the first time, there is still a vibration. So its back in again today. They said it might be the drive shaft causing the issue due to the 2 inch lift, or there is still something wrong with the tires. They have a road force balance machine at this dealership. Has anyone else experienced this? If so what was the solution?
Thanking you in advance.
T

[jbplock]

T,

What body style is your truck .. crew cab, ext cab? Also is the vibration speed dependant? There have been reports of some vibration problems .. Try searching this forum for “vibration”.

One common problem I’m familiar with is called “ frame beaming” (TSB 1844688). It’s a beam shake vibration that is usually felt in the seat and occurs between 40-60 mph. Severity of the shake may vary from vehicle to vehicle. The diagnostic procedure says to place 200-500 lbs in the bed and if the shake goes away, it’s “beam shake”. The TSB further states it’s a characteristic of the vehicle and that there is no fix (for the 2500/3500HD’s).

On my 03 crew cab I get a slight bounce type vibration at approximately 45mph when the bed is unloaded.. In the winter I run with four 80lb sand bags in the bed and the vibration is gone.

I also had problems with out-of-round tires casuing vibrations on my 98 K3500 Crew Cab Dually LB. New tires cured the vibration.

:)

[Mark Rinker]

Add a combo fuel tank/tool box in the bed and run it full. That should help, if it is 'beam shake'. I keep mine full in my 2002 because the empty ride is so much nicer with ~600 lbs of fuel 'amidships' on the truck.

[titanite]

It is a classic 2007, crew cab shortbox. Seems like the vibration is the worst at about 75km/hr , 45miles/hr. I dont recall having the shake when it was stock (but I only drove it for about 1000km before switching tires) with stock 245R16E tires. I had the dealership do a 2 inch lift and put the 285R16E tires on it. So either those tires and lift has made this vibration worse or it was never there before, I dont know. I am going to have another tire shop do a road force balance on the tires tomorrow as a second opinion and go from there. This shop will actually provide a diagnostic print out on the tire and rims, where as GM dealer just says, "They are balanced" and the shop managers comments are "Vibration is acceptable for 2500 hd with oversize tires". I dont think any vibration is acceptable. If it is a problem with the truck and its not fixable, fine, but if its a balance problem they are too lazy to sort out, they can take the tires back.
Thank you for the info guys, I'll post what I find out.
T.

[DmaxMaverick]

Many possibilities. To start with, when you have problems like this, you should "undo" what you did when the problem appeared. Install a set of OEM tires/wheels and try to duplicate. If you can duplicate the problem in OEM trim, then it's the dealer's responsibility to correct it. If it is found to be caused by the new tires/wheels or the lift, then it's your responsibility to work with the aftermarket company for a solution. The dealership, even though they did the work, will get no support from GM for aftermarket suspension mods. Did you install the new tires on the OEM wheels? If so, the tires are too wide for the wheels, according to BFG. If it's the same with either tire/wheel, then suspect the lift. It's likely the driveshaft angle is out of spec, and can be adjusted with a wedge under the leaf springs. If you have blocks in the rear, consider tossing the blocks and re-arc the springs or use extended or relocated shackles for the lift. Blocks, although they are popular, are a common cause for these types of problems because they change the dynamics of the rear suspension. Also, just because the tires/wheels balance doesn't mean they are round, or don't have a flaw in the cord construction, which will cause vibrations. Jack the rear and watch the tires as they rotate under engine power. Any variation in roundness or tread tracking will be suspect.