Shake or Vibration Issues

[C6Bill]

Anyone here have an ATV to throw in the back to test that out ? Unfortunately I sold my Rincon a few months ago

Edited September 13, 2015 by C6Bill

[abominable z71]

Found the parts breakdown drawings for the front drive shafts. Inner joint that connects to the diff is a tripot, outer joint with the stub shaft that holds the front hub assembly together is a 6 ball rzeppa joint.

[Wrench589]

Getting pretty technical!

 

There is definitely something going on in the front end of these vehicles. On our Yukon XL, I can always feel a slight vibration in 2wd. When I put it in 4auto, the vibration is worse. I believe that in 4auto, the transfer case shifts into 4wd and the front propshaft and differential spins, and there are clutches in the output of the differential,case that lock up when the system goes into 4wd. I don't notice any difference in vibration between 4auto and 4high.

 

But don't forget, there still some vibration even in 2wd, so not sure what to make of it. Unless....it's all in the differentials. Both of them. In 2wd, I'm only feeling vibs from the rear diff. In 4auto/4high, I'm feeling vibs from both. Hmmmm. Maybe I'm on to something.....

[STAYBG]

typically pinion angle causes issues at lower speeds but with these trucks there is no telling what might happen. In a perfect world the working angles between the front and rear joint should cancel one another out or be as close to zero as possible. If the front slip yoke tips down 5 degrees your pinion yoke at the rear end should tip up 5 degrees so that the u joint speeds cancel one another out. With a heavy load as the springs flatten out the rear shackle swings backward to allow the spring to lengthen. Because the rear shackle is on a fixed pivot and the front spring eye is stationary the height between the 2 eyes changes causing the pumpkin to rotate changing the working angle between the front and rear u joints. This could be mitigating the vibration if it's rotating the pinion into a better working angle relationship. The other possibility is the additional weight has changed the natural frequency of the truck enough to eliminate the resonate frequency. Natural frequency is the square root of k/m where k is the stiffness matrix for the vehicle (impossible to calculate by hand as it requires FEA on a seriously powerful computer) and m is the mass. The additional weight of the plywood changes the ratio and ultimately changes the natural frequency for the truck. If you look at the tacoma narrows bridge failure in the 1940s this a perfect example of resonance. The wind coming through the narrows matched the natural frequency of the bridge and catastrophic failure ensued. I've noticed that having 4 200lb people in my truck 600lbs more than normal that the vibration is significantly reduced as well.

i have a vibration on hard acceleration from a dead stop also.. Edited September 13, 2015 by STAYBG

[fireaxxe]

So I just got word that my 2nd Silverado also has a bad rear axle assembly. Going to be in the shop for a week.

 

Any of you that haven't checked for this...drive on the highway, then exit on the smoothest exit ramp you can find. As you decelerate to 50mph you will start feeling a rumble or vibration in the truck, especially in the steering wheel. This is your ring/pinion gears grinding due to excessive backlash. If this isn't fixed, your rear differential could be ready to fail about the time your warranty is expiring!

 

This can only be felt during deceleration, when there is no torque being applied to the differential gears.

 

I have been experimenting with this over the last few days and have found that the driveline angles are off. I have the same exact symptom as you. Other than this one issue the truck rides perfectly smooth. Tires are true and there is no shake at all at highway speeds. But when I am decelerating with no brakes there is a vibration that is felt and is accompanied with a roaring sound like a badly cupped tire except it oscilates more. This vibration is worst from approximately 52mph down to 40mph. I can also feel this in the steering wheel and seat. Now here is the kicker if I shim the rear axle and angle it up, the vibration diminishes. Untouched, the vibration that I feel is about a 7 but when I shim the rear axle its about a 3. This slight vibration never totally goes away I think its the pinion/ring gear backlash but thats not the only issue. The slack in the rear end is agitated overtime by the bad driveline angles and this causes increased wear. This with also increase wear on U-Joints, bearings and seals. If the rear axle is replaced and the pinion angle, along with the slip yolk angle are not corrected and phased correctly iwth the driveshaft, this will be a recurring issue. I am getting a second opinion from an independent 4 wheel drive shop and will share this information.

[fireaxxe]

Also maybe this is proof that the 75w-85 synthetic rear axle fluid is a tad bit too thin for these trucks. Im willing to bet if you change the fluid to a standard 80w-90 fluid this would cushion the gears and reduce some of the vibration for a few thousand miles.

[Aaron1085]

So as you know, I went thru this same issue. I filed a complaint with BBB, traveled 300 miles out of my way to other dealership for 4 trips that never fixed the issue. Went back to home dealership and co tinier to raise hell between GM and BBB and face to face contact with sales manager and service manager. District manager was only decent once the Salas Manager climbed in his ass and the DSM ass. There is alittle more to it but basically I was as polite, rude, distraught and direct as needed for each situation. I voiced my concerns regarding the price of the truck and the incredibly poor GM customer service that frankly, is laughable.

 

Had it not been for the sales manager stepping up and wanting to keep me as a customer and shockingly, the service manager who had more pull with the DSM than I thought and was PUSHED by the sales manager, I would not have gotten into a new truck for hardly any out of pocket.

 

Forget that GM will do anything for you...they won't. Rely on local bosses and find a deal (ie: 20% trucks, etc). It may not be exactly the truck you want, but if it's 99% good to you, seize the deal.

 

 

Sent from my iPhone

[MBalck]

Well guys my truck is back in the shop for the fourth and final time before I am forced to make this an even bigger mess. Nonetheless they gave me a 2015 GMC CC 2wd SLE as a loaner .....surprise to no one I'm sure....this POS shakes like hell on anything over 65. Just wanted to pass the word. I'll be taking my loaner in on Monday to inform the SM of the issue with this truck as well.

[abominable z71]

i have a vibration on hard acceleration from a dead stop also..

The pinion angle changes during acceleration and deceleration due to spring wrap in the leafs, clamping the springs helps eliminate it but changes the ride because it hampers the progressive rates of the springs. Traction bars help eliminate spring wrap. Another option is to put put a cv joint on the slip yoke end. Common solution on the front drive shaft of awd my understanding is that it's a must on lifted trucks with awd like the 2008 -2013 Denali pickups otherwise they vibrate.

[abominable z71]

Well guys my truck is back in the shop for the fourth and final time before I am forced to make this an even bigger mess. Nonetheless they gave me a 2015 GMC CC 2wd SLE as a loaner .....surprise to no one I'm sure....this POS shakes like hell on anything over 65. Just wanted to pass the word. I'll be taking my loaner in on Monday to inform the SM of the issue with this truck as well.

Do you feel the vibration in the steering wheel on the 2wd, or is it mainly floorboard/seat/center console?

[LongrangeLauber]

The pinion angle changes during acceleration and deceleration due to spring wrap in the leafs, clamping the springs helps eliminate it but changes the ride because it hampers the progressive rates of the springs. Traction bars help eliminate spring wrap. Another option is to put put a cv joint on the slip yoke end. Common solution on the front drive shaft of awd my understanding is that it's a must on lifted trucks with awd like the 2008 -2013 Denali pickups otherwise they vibrate.

Yes indeed. When I lifted my 02 it was a must (front shaft always spun). Thought it was from the new gears installed but it was just from the flex at the one joint

[abominable z71]

So as you know, I went thru this same issue. I filed a complaint with BBB, traveled 300 miles out of my way to other dealership for 4 trips that never fixed the issue. Went back to home dealership and co tinier to raise hell between GM and BBB and face to face contact with sales manager and service manager. District manager was only decent once the Salas Manager climbed in his ass and the DSM ass. There is alittle more to it but basically I was as polite, rude, distraught and direct as needed for each situation. I voiced my concerns regarding the price of the truck and the incredibly poor GM customer service that frankly, is laughable.

 

Had it not been for the sales manager stepping up and wanting to keep me as a customer and shockingly, the service manager who had more pull with the DSM than I thought and was PUSHED by the sales manager, I would not have gotten into a new truck for hardly any out of pocket.

 

Forget that GM will do anything for you...they won't. Rely on local bosses and find a deal (ie: 20% trucks, etc). It may not be exactly the truck you want, but if it's 99% good to you, seize the deal.

 

 

Sent from my iPhone

Hows the new truck ride?

[MBalck]

Do you feel the vibration in the steering wheel on the 2wd, or is it mainly floorboard/seat/center console?

 

The vibration is in the seats, steering wheel, console, back seats and in the dash. It's pretty bad, almost as bad as my actual truck.

[abominable z71]

I'm tempted to put a tow bar on the truck and pull out all the rear drive line and front cv shafts then tow this thing at 70 mph to eliminate a large portion of the drive train as the potential cause. If the vibe is still there its wheels and tires, hubs, rear axles. or diff related. Vibe goes away, put the rear drive shaft in, if the vibe is back it's likely the drive shaft, u joints / working angles or slip yoke.

[MBalck]

That's definitely one way of narrowing down the issue.....helluva idea