Shake or Vibration Issues

[pm26]

hey guys, well there is now a recall for the trailer hitches on the Silverado's apparently the welds can weaken more than is allowed and cause people to die.... maybe GM should be in the business of killing.... they seem better at that than building trucks.... check your trucks everyone, my understanding is that it is the Z71 and Max trailering package trucks

It sounds like GM is buying these hitches from harborfreight (or equivalent quality supplier).

Edited February 21, 2016 by pm26

[ekimsinnigcm]

It sounds likes GM is buying these hitches from harborfreight (or equivalent quality supplier).

 

Almost makes one wonder if this is the cause of the vibration and GM is rolling out in this manner so most customers don't go looking for a vibration instead of "Trailer hitches cause vibrations is "x" model Silverado and Sierras". Food for thought, especially after all of this time one would think there would have been a lot of broken trailer hitches by now if that's the case.

[Wrench589]

I think the problem with doing an assembly is there is that it can't differentiate whether the tire or rim is the source or both in combination. I'd really love to talk to a design engineer from hunter to talk about the machines capabilities. What I do know, the compression arm can provide a variable force onto the tire up to 1250 lbs, it's resolution is .01 Oz or about 1/4 gram and placement accuracy is +/- .35 degrees. Not sure what it can tell you when it comes to higher order vibrations. I checked the vibrations on the console, seat and steering column at various speeds from 60 to 76 mph always 3rd order tire, checked same speeds in 4th 5th and 6th gear no affect on the vibration. I wish I knew someone with more sophisticated equipment I could borrow to really do some testing and try to narrow down the source. I think even a single channel eva could do it , even though it would be much faster with a 4 channel device.

No, it can't differentiate between rim or tire from a simple Road Force measurement. But, if the operator follows the instruction in Hunters manual, it can. Step one is to mount the bare wheel (no tire) on the machine and measure the bead runout is (inner and out). This is indexed to a reference (typically the valve stem). The roller is no used, of course, but the reality is, the stiffness of the wheel in likely going to be consistency all the way around.

 

Next, mount the tire.

 

Next, measure the Road Force Variation. By then comparing the results of the combined RFV to the wheel runout, the machine can determine if the final is tire or wheel, and where the tire should be rotated to relative to the wheel to minimize the total combined.

 

Here is the catch....if the wheel has 0 runout, then there is absolutely no opportunity to improve the combined total. Stuck with whatever the tire produces.

 

As for the machine itself, the roller arm does not take any measurements. It simply applies a force to the tire to deflect/load it similar to on a vehicle going down a road. I say similar because there are two fundamental differences that even Hunetr does not talk about. First, the roller is round, whilst the road is flat. There floor, the deflection pattern of he tread will be different. Second, the tire is spinning at a much lower speed than you are driving at. How much difference does that make, of what kind of errors could that result in? Don't know.

 

What the machine does measure is vibration of the main shaft. It measures it in two locations along the shaft, likely beside the bearings, and knowing the various distances of the machine and the tire/wheel, it can calculate out of balance at the selected correction planes. This information can also be used for the Road Force Variation calculations, based on a known load of the roller. The RF result is expressed in LB, and from what I understand, Hunter expresses it that way to relate it to the amount of shaking force that would be generated at a reference speed with much that RFV. One could back calculate that to an equivalent static unbalance, for example, to get a better feel for it and it would be in the oz's, as we are used to seeing it.

 

The specs on the Hunetr are relative to doing the dynamic balancing portion, but are related to the RF, as the same sensors are doing that too.

 

Back to your truck, if the peak vibration is tracking 3x tire speed, then it it not a resonance. That should come and go at the specific natural frequency. Now, many resonances do have a bandwidth associated with them, because of some damping in the system - does yours start at a speed, get worse to a peak, them diminish back to very low again? If so, that could be a resonance. If it just keeps getting higher and higher in amplitude as speed increases, that is usually simple mass unbalance.

[pm26]

Let's get back to wheel balancing fundamentals. You can balance wheels completely wrong even with a Hunter 9700 brand new balancer for the following reasons:

 

1. The machine must be recently calibrated to ensure proper balancing. Calibration on Hunter 9700 machine is done by screwing a calibration metal stick into threaded holes of the wheel mounting flange and running through short calibration cycle. It is a lot quicker and easier than calibration methods on other balancer that require a wheel to be mounted on the balancer and a calibration weight of known mass to be hammered on the wheel at several locations during the calibration cycle. If the balancer is not recently calibrated or calibrated wrong, forget good balancing results.

 

2. Properly mounting of a wheel on a machine is of utmost importance. I have already posted about some pitfalls with cones of wrong size. Flange plates that hold the wheel by the lugnuts produce the best and most consistent results. It is ironic that Hunter does not recommend performing road force balancing on their 9700 series balancers by using centering cones only. Yet, they do not supply flange plates with their machines (flange plates are a pricey optional accessory). I question accuracy of road force measurements done with the wheel mounted with centering cone only. Do GM dealers perform road force measurements by using flange plates?

 

3. I have seen wheels balanced totally wrong on a Hunter 9700 balancer (as much as 1 oz out on an 18 inch diameter passenger car wheel) because of improper calibration and improper wheel centering . The bigger the wheel diameter and the lower profile the tire, the more difficult it is to properly balance such a tire.

 

And finally, quality of the tires is a huge variable. In some cheaply made tires, steel belts can literally come loose and shift when the tire gets hot and this will throw the tire out of balance under high speed sustained driving conditions. I actually had two Michelin tires, 15 inch size on my Mazda years ago that did this and no amount of balancing could help the problem.

Edited February 21, 2016 by pm26

[mjj]

 

Almost makes one wonder if this is the cause of the vibration and GM is rolling out in this manner so most customers don't go looking for a vibration instead of "Trailer hitches cause vibrations is "x" model Silverado and Sierras". Food for thought, especially after all of this time one would think there would have been a lot of broken trailer hitches by now if that's the case.

Or the opposite. The vibrations are now starting to crack the welds on the hitches. People were worried what the vibrations would do long term. This could be the start of the long term effects.

 

But I like where you're going with your idea. If these new hitches look different and bolt up differently to the frames one could speculate alternative motives. Let the rummors begin! Lol

Edited February 21, 2016 by mjj

[tnchevy]

I seriously doubt the vibrations are causing hitches to crack. I drive on alot of deep muddy logging roads for a living and then hop on the interstate to come home. The rims are usually full of mud which makes my work truck out of balance most of the time and shakes can be pretty bad doing 75 mph. After 20 years of this never had a hitch crack or my front brushguards or winches to shake loose. Others have also claimed the vibes have not been fixed on the 2016 models and the recall does not effect them.

[chrisfg]

i feel like i am on the same boot with you every time i read a page of post i feel like i am hearing my self explain what is going on with my truck except one thing. my vibration started from day one with the first mile. i have even had 4 sets of tires put on the truck in 2 weeks. my truck is 2015 z71 4x4 LT. is there a fix for this yet i bought 2 Chevy on the same day and i am miserable. my wife will not ride in the truck because it gives her a migraine from the vibration.

[DALaws]

Update: Dealer told me they replaced all four wheels with 4 wheels that took from one on their lot. They claimed this fixed the vibration and decided to replace all 4 tires on My original rims. They say all is fine now. As you may recall from my previous post, there certainly is a lot less vibration, But I still get a slight shake at 65 to 75. I called dealer back and explained that the truck still has a vibration. He told me he would have his shop foreman call me.? Well guess what, no phone call. Not sure what the shop foreman was going to tell me? I have a sense I may be stuck with a vibrator.

 

I am beginning to believe that since the 14' re-design, this may be the new normal in Q/C in their trucks. Think about it,, they sell a bunch of them and are profitable, Q/C may tend to be a bit overlooked. For those of you older people, this was true beginning in the early 70's to mid 80's. GM was cranking out cars, but they were unreliable to say the least. It was not until the Japanese started to introduce cars to the American market, GM finally woke up and started putting out more reliable vehicles.

 

I hope I am proven wrong, I have been a Loyal GM guy even when they put out crappy vehicles. They have always produced decent drive lines, the rest of parts, very poor. I will stay loyal to GM because I think when autos sales slow down, Q/C will increase and put out consistently well engineered vehicles. This is especially to be true of trucks, they sell so many of them.

 

In conclusion, my Wife now requires very long trips at higher speeds to get her rev'd up. Before, I could just go around the block. Damn GM, costing m more gas & and time to get things going down there.

[Jesse Davidson]

Update: Dealer told me they replaced all four wheels with 4 wheels that took from one on their lot. They claimed this fixed the vibration and decided to replace all 4 tires on My original rims. They say all is fine now. As you may recall from my previous post, there certainly is a lot less vibration, But I still get a slight shake at 65 to 75. I called dealer back and explained that the truck still has a vibration. He told me he would have his shop foreman call me.? Well guess what, no phone call. Not sure what the shop foreman was going to tell me? I have a sense I may be stuck with a vibrator.

 

I am beginning to believe that since the 14' re-design, this may be the new normal in Q/C in their trucks. Think about it,, they sell a bunch of them and are profitable, Q/C may tend to be a bit overlooked. For those of you older people, this was true beginning in the early 70's to mid 80's. GM was cranking out cars, but they were unreliable to say the least. It was not until the Japanese started to introduce cars to the American market, GM finally woke up and started putting out more reliable vehicles.

 

I hope I am proven wrong, I have been a Loyal GM guy even when they put out crappy vehicles. They have always produced decent drive lines, the rest of parts, very poor. I will stay loyal to GM because I think when autos sales slow down, Q/C will increase and put out consistently well engineered vehicles. This is especially to be true of trucks, they sell so many of them.

 

In conclusion, my Wife now requires very long trips at higher speeds to get her rev'd up. Before, I could just go around the block. Damn GM, costing m more gas & and time to get things going down there.

awww poor guy lol

[abominable z71]

No, it can't differentiate between rim or tire from a simple Road Force measurement. But, if the operator follows the instruction in Hunters manual, it can. Step one is to mount the bare wheel (no tire) on the machine and measure the bead runout is (inner and out). This is indexed to a reference (typically the valve stem). The roller is no used, of course, but the reality is, the stiffness of the wheel in likely going to be consistency all the way around.

 

Next, mount the tire.

 

Next, measure the Road Force Variation. By then comparing the results of the combined RFV to the wheel runout, the machine can determine if the final is tire or wheel, and where the tire should be rotated to relative to the wheel to minimize the total combined.

 

Here is the catch....if the wheel has 0 runout, then there is absolutely no opportunity to improve the combined total. Stuck with whatever the tire produces.

 

As for the machine itself, the roller arm does not take any measurements. It simply applies a force to the tire to deflect/load it similar to on a vehicle going down a road. I say similar because there are two fundamental differences that even Hunetr does not talk about. First, the roller is round, whilst the road is flat. There floor, the deflection pattern of he tread will be different. Second, the tire is spinning at a much lower speed than you are driving at. How much difference does that make, of what kind of errors could that result in? Don't know.

 

What the machine does measure is vibration of the main shaft. It measures it in two locations along the shaft, likely beside the bearings, and knowing the various distances of the machine and the tire/wheel, it can calculate out of balance at the selected correction planes. This information can also be used for the Road Force Variation calculations, based on a known load of the roller. The RF result is expressed in LB, and from what I understand, Hunter expresses it that way to relate it to the amount of shaking force that would be generated at a reference speed with much that RFV. One could back calculate that to an equivalent static unbalance, for example, to get a better feel for it and it would be in the oz's, as we are used to seeing it.

 

The specs on the Hunetr are relative to doing the dynamic balancing portion, but are related to the RF, as the same sensors are doing that too.

 

Back to your truck, if the peak vibration is tracking 3x tire speed, then it it not a resonance. That should come and go at the specific natural frequency. Now, many resonances do have a bandwidth associated with them, because of some damping in the system - does yours start at a speed, get worse to a peak, them diminish back to very low again? If so, that could be a resonance. If it just keeps getting higher and higher in amplitude as speed increases, that is usually simple mass unbalance.

The third order tire vibration is always there but even though it can be detected by an accelerometer at all speeds it can't be felt until 72mph, peaks in intensity at 76 mph and falls off at just above 80 mph. The vibration we all feel in these trucsk is always there at all speeds it's amplitude is just so small at other speeds we don't feel it.

[Jesse Davidson]

The third order tire vibration is always there but even though it can be detected by an accelerometer at all speeds it can't be felt until 72mph, peaks in intensity at 76 mph and falls off at just above 80 mph. The vibration we all feel in these trucsk is always there at all speeds it's amplitude is just so small at other speeds we don't feel it.

speak for yourself, My truck gets it at multiple speeds, not just 70-76

[taps929]

hey all - fun day here - recap on mine (ive posted in the past) - got the vibe - they had replaced shocks - tires - rf'd multi times - new shaft - shim game for pinion angle - yadda yadda - still had the vibe in the end - well today my 14 silverados rear end locked up - all I heard was a loud bang then the tires locking up - just finished watching it get dragged onto the back of a flat bed - the scary part is, I just got off the highway from dropping my kids off to their moms house - I couldn't imagine it happening at 70-75 mph - I'm done with this truck - I will update their findings in the am when they call - I'm guessing the ring gear blew - we shall see- and it did it at 22,112 miles on it -

Edited February 22, 2016 by taps929

[LongrangeLauber]

hey all - fun day here - recap on mine (ive posted in the past) - got the vibe - they had replaced shocks - tires - rf'd multi times - new shaft - shim game for pinion angle - yadda yadda - still had the vibe in the end - well today my 14 silverados rear end locked up - all I heard was a loud bang then the tires locking up - just finished watching it get dragged onto the back of a flat bed - the scary part is, I just got off the highway from dropping my kids off to their moms house - I couldn't imagine it happening at 70-75 mph - I'm done with this truck - I will update their findings in the am when they call - I'm guessing the ring gear blew - we shall see-

My pinion blew in my 02 and did the same thing

[Txjose]

hey all - fun day here - recap on mine (ive posted in the past) - got the vibe - they had replaced shocks - tires - rf'd multi times - new shaft - shim game for pinion angle - yadda yadda - still had the vibe in the end - well today my 14 silverados rear end locked up - all I heard was a loud bang then the tires locking up - just finished watching it get dragged onto the back of a flat bed - the scary part is, I just got off the highway from dropping my kids off to their moms house - I couldn't imagine it happening at 70-75 mph - I'm done with this truck - I will update their findings in the am when they call - I'm guessing the ring gear blew - we shall see- and it did it at 22,112 miles on it -

Holy shit!!!

 

Glad everyone is safe!!

 

Need new pair of undies?

 

Sent from my Note 4 on Tapashit

[taps929]

thanks - everyone is good - but went commando - so new pants, socks and shoes are in order -