Shake or Vibration Issues

[Wrench589]

The PSD is the power spectrum density . It is what you think, takes the square of frequency divided by the frequency that it occurs. I was more curious as to the frequency which the primary vibration occurs than the amplitude of the vibration to try and narrow down which part could possibly be the source. The readings in the graph were taken at 76 mph. First order vibration at 13.3 second at 26.6 and third at 39.9 and the first order drive line would be 45.5. Taking into account it is just an accelerometer in a phone, mounting, the FFT algorithm and truck speedometer accuracy the results are pretty much spot on for the vehicle speed, small spikes at 13, 27 and 40 and a small drive line vibe at 46 Hz. Its pretty safe to say the vibration is a third order related to the tire angular velocity. To test the app I induced a large drive line vibration by putting a few hose clamps on it and it indeed generated a larger spike and caused a beating vibration when it combined with the 40 Hz what was really interesting is even with a significant amount of unbalance on the drive line the PSD at 46 hz was still nowhere near as large as it was at 40. The tires have less than 10 lbs force variation checked on 2 different machines at different shops they have been trued and balanced on the vehicle (lateral and radial run out were low even before truing) and it continues to vibrate I keep going back to the rear end because its the only assembly that has parts turning at the same velocity as the tires that also have surface contact that could generate something third order that and the front hub bearings it just seems like a bearing issue would have gotten much worse after 15k miles. Assuming the data is accurate what besides tires caould cause it, any thoughts Wrench? A few people claim a fix after replacing the rear some said it was only temp and the vibe came back. It's maddening I tell you.

Is 13.3 hz the tire first order?

 

Well, not 100% sure what 3rd order tire would be. I think there was a GM bulletin that outline what could be 1st, 2nd and 3rd order but I can't recall what s said. Seems to me, 3rd order is not typically associated with card an joints. But on the tire side, not sure.

 

Now, one thing that is important to note is that I am pretty sure that GMs Road Force spec only applies to the 1st order disturbance. If that is true, and the typically vibration is 3rd order, then all this pissing around with Road Force at the dealer is a waste of time if they are not looking at 2nd and 3rd order RFV and eliminated that too.

 

Maybe it does all go back to tires....

[abominable z71]

Is 13.3 hz the tire first order?

 

Well, not 100% sure what 3rd order tire would be. I think there was a GM bulletin that outline what could be 1st, 2nd and 3rd order but I can't recall what s said. Seems to me, 3rd order is not typically associated with card an joints. But on the tire side, not sure.

 

Now, one thing that is important to note is that I am pretty sure that GMs Road Force spec only applies to the 1st order disturbance. If that is true, and the typically vibration is 3rd order, then all this pissing around with Road Force at the dealer is a waste of time if they are not looking at 2nd and 3rd order RFV and eliminated that too.

 

Maybe it does all go back to tires....

It is my understanding from the owner of a hunter road force touch that the machine is not capable of diagnosing anything third order, and it cannot do a second order on a wheel/tire assembly only a wheel by itself. It's been a while since I had this discussion with him but I believe this is what he said. Typically 2nd and 3rd order tire vibrations diminish in amplitude compared to the first order and no one worries about them that is until you put it on a truck with a natural frequency that matches it and you get harmonic resonance. Changing the mass of the system can shift the natural frequency and that's probably what happened to the guy that had 5 people in the truck with the arbitrator, when he was told there's no vibration. When I have 4 adults in the cab (roughly 800-850 lbs) There is very little vibration felt. Perhaps I just need to replace the floor board with 1/2" steel plate

[14silverado4.3]

That's exactly what he said on the tires, it was a phase 3, meaning the tire was out of round in 3 spots he said. He said it was the right front.

Holy shit, mine is the right front also. Same PICO reading! Pointed to right front.

[Jesse Davidson]

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

[Wrench589]

It is my understanding from the owner of a hunter road force touch that the machine is not capable of diagnosing anything third order, and it cannot do a second order on a wheel/tire assembly only a wheel by itself. It's been a while since I had this discussion with him but I believe this is what he said. Typically 2nd and 3rd order tire vibrations diminish in amplitude compared to the first order and no one worries about them that is until you put it on a truck with a natural frequency that matches it and you get harmonic resonance. Changing the mass of the system can shift the natural frequency and that's probably what happened to the guy that had 5 people in the truck with the arbitrator, when he was told there's no vibration. When I have 4 adults in the cab (roughly 800-850 lbs) There is very little vibration felt. Perhaps I just need to replace the floor board with 1/2" steel plate

When you say "and it cannot do a second order on a wheel/tire assembly", do you mean can't measure it or can't correct for it? And why can it do a wheel by itself? I would think the machine can measure both 1st order and 2nd order regardless of wheel only or wheel/tire. Correction would be another matter - based on Force Matching I would think can only correct for 1st order if both the wheel and tire have some 1st order RFV that can be matched up to cancel each other. I guess in theory, the same could be done for a 2nd order, but what is the chance that a tire and and wheel both have a 2nd order defect that can cancel each other out!

 

Certainly even a small amount of 3rd order could excite an natural frequency that is at that same frequency, especially if that natural frequency is very lightly damped. Still not sure what generates a 3rd order tire freq, but in theory, many fundamental frequency generate harmonics albeit quite small amplitude compared to the fundamental.

 

Where did you put the phone to get the vibration readings? On the console?

 

Have you done any bumps tests to confirm the console natural frequency (if that where you measured it)?

[tnchevy]

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

Dang Jesse D, you need to get over your piece of crap truck and move on with your life. Every manufacturer has or has had recalls on their trucks on things that could possibly kill you (tacomas with rotting frames, fords with leaking master cylinders that could catch fire, etc.)

[Juicybusa]

I'm certain that's what GM would like for him to do. If more customers held their feet to the fire, quality would improve.

[Jesse Davidson]

Dang Jesse D, you need to get over your piece of crap truck and move on with your life. Every manufacturer has or has had recalls on their trucks on things that could possibly kill you (tacomas with rotting frames, fords with leaking master cylinders that could catch fire, etc.)

 

It cost money to move on.... If they give me the money, I will gladly move on!

I'm not saying that other manufacturers don't have recalls, what I am saying is that the amount of issues and recalls that GM has had in recent years is beyond absurd. Some of the lawyers I have spoken with have even said how sh*tty GM has become and how the suits against them for lemon law cases have risen what I believe was 46% or 56% or something like that over the last 2 years.... Now the most of any manufacturer.

 

I do apologize for the comment about GM being better at killing than building vehicles.... Finding out about ANOTHER issue just really pissed me off

 

I'm certain that's what GM would like for him to do. If more customers held their feet to the fire, quality would improve.

Thank you for he support

[The Zip]

I'm certain that's what GM would like for him to do. If more customers held their feet to the fire, quality would improve.

Folks on this thread with problems is not looking for quality to improve, just quality would be a good start.

[Bowtie619]

Hey guys,

 

Wow, this thread is long!

 

I just picked up a 2014 LTZ Silverado from a private party (Warranty Voided). During inspection the dealership noted some small vibrations when he got up to around 65-75 mph and showed me a dent in the drive shaft that he thought was causing it. I just found this thread and now it's looking like this is a common issue with the Silverado (How Disappointing!!) Anyways, I have already ordered part number 2325118 from gmpartsonline and now I'm wondering if I should even install the part or just send it back.

 

Can anyone confirm that they replaced the drive shaft and this was a fix for the vibrating issue? I don't want to pay 350 and it does not even resolve the problem. It should be easy enough to put on so I'd be happy to put it on and report back if I notice any changes.

 

Sorry if this has been discussed or tried already in the previous 500 pages lol....

[Jesse Davidson]

Hey guys,

 

Wow, this thread is long!

 

I just picked up a 2014 LTZ Silverado from a private party (Warranty Voided). During inspection the dealership noted some small vibrations when he got up to around 65-75 mph and showed me a dent in the drive shaft that he thought was causing it. I just found this thread and now it's looking like this is a common issue with the Silverado (How Disappointing!!) Anyways, I have already ordered part number 2325118 from gmpartsonline and now I'm wondering if I should even install the part or just send it back.

 

Can anyone confirm that they replaced the drive shaft and this was a fix for the vibrating issue? I don't want to pay 350 and it does not even resolve the problem. It should be easy enough to put on so I'd be happy to put it on and report back if I notice any changes.

 

Sorry if this has been discussed or tried already in the previous 500 pages lol....

Sorry to be the bearer of bad news, but if I remember correctly, in this entire thread I think only one person has had the driveshaft even help. Here have been a lot of people that have had their driveshafts replaced and rebalanced with basically no resolutions.

Folks on this thread with problems is not looking for quality to improve, just quality would be a good start.

First and foremost we are looking for our issues to be fixed or our money back... Neither is likely

[abominable z71]

When you say "and it cannot do a second order on a wheel/tire assembly", do you mean can't measure it or can't correct for it? And why can it do a wheel by itself? I would think the machine can measure both 1st order and 2nd order regardless of wheel only or wheel/tire. Correction would be another matter - based on Force Matching I would think can only correct for 1st order if both the wheel and tire have some 1st order RFV that can be matched up to cancel each other. I guess in theory, the same could be done for a 2nd order, but what is the chance that a tire and and wheel both have a 2nd order defect that can cancel each other out!

 

Certainly even a small amount of 3rd order could excite an natural frequency that is at that same frequency, especially if that natural frequency is very lightly damped. Still not sure what generates a 3rd order tire freq, but in theory, many fundamental frequency generate harmonics albeit quite small amplitude compared to the fundamental.

 

Where did you put the phone to get the vibration readings? On the console?

 

Have you done any bumps tests to confirm the console natural frequency (if that where you measured it)?

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.

[tnchevy]

It cost money to move on.... If they give me the money, I will gladly move on!

I'm not saying that other manufacturers don't have recalls, what I am saying is that the amount of issues and recalls that GM has had in recent years is beyond absurd. Some of the lawyers I have spoken with have even said how sh*tty GM has become and how the suits against them for lemon law cases have risen what I believe was 46% or 56% or something like that over the last 2 years.... Now the most of any manufacturer.

 

I do apologize for the comment about GM being better at killing than building vehicles.... Finding out about ANOTHER issue just really pissed me off

 

 

Thank you for he support

Yes it does cost money to move on but sometimes paying the money and being happy is the best route. If you think the recalls on our trucks is bad try owning a an early build of the new model Jeep Grand Cherokee like I do. If your chevy has you this upset then the Jeep would send you to the hospital. That thing has had a major recall every few months since we have owned it. Has not let me down, drove it out to Idaho and back to TN a couple of times now.

[Bowtie619]

Sorry to be the bearer of bad news, but if I remember correctly, in this entire thread I think only one person has had the driveshaft even help. Here have been a lot of people that have had their driveshafts replaced and rebalanced with basically no resolutions.

 

First and foremost we are looking for our issues to be fixed or our money back... Neither is likely

Well Damn!! Thanks for the info, It should be fairly easy to bolt on so I'll report back if I notice a difference. If not I'll return it...

[pm26]

http://www.ijser.org/researchpaper/analysis-of-vibrations-of-automobile-suspension-system-using-full-car-model.pdf

 

 

Edited February 20, 2016 by pm26