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slopra

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    San Antonio, TX
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    Male
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    2017 Denali Ultimate CC Std Box 6.2L

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  1. Traded in my 16 SLE last night for this beauty! 17 Denali Ultimate CC Standard Box 6.2L
  2. Shake, vibration, shimmy, jiggle, whatever you want to call it, it's all the same thing. The oscillating component that's causing you to feel something is producing a frequency. That frequency directly correlates to whatever you're feeling. You then measure that frequency and can use the speed you were traveling/what gear you were in, to determine what could have produced that frequency. If I'm feeling a 10-14hz frequency at highway speeds, I know that it simply isn't possible for that to be coming from the driveshaft. That can only be coming from something in the wheel assembly. No one is discounting your findings, we have no idea what the frequency of your shake was anyway. (the dealership definitely found something with the pico meter, they just didn't know what to do most likely. that or they didn't install it right) The issue is you arguing the fact that every one of these trucks with a vibration issue is having a driveshaft issue...that's a ridiculous claim. I totally agree with you that new body mounts is only going to mask the real problem. It could reduce the vibrations transferred to the cab in theory, but the oscillating component is going to keep on doing so, which is only going to damage other components on the truck. With the many many different vibration symptoms owners are reporting I truly believe that GM just has a QA problem. The part manufacturers could have poor QA or poor tolerances, or GM could be installing parts wrong, but at the end of it all GM QA should catch any of it, or a good chunk of it at least.
  3. That makes you sound even more ridiculous for saying and yelling over and over that the driveshaft is the issue. If you were part of the 600 pages then you would know, as Newell33 and Brianibew have already pointed out, that checking for runout/balance and then balancing or replacing accordingly has only fixed a small percentage of vibration issues in these trucks. Congrats on finding the source of vibration with your truck and thanks for sharing. But quit trying to shove it down people's throat and then getting upset when people don't acknowledge you. You haven't contributed anything by just yelling DRIVESHAFT in this and every other vibration thread you bumped. It's very obvious that there are many many things causing vibrations in these trucks. I think the goal here should be to simply give everyone the knowledge to properly diagnose which is exactly what I've been trying to do.
  4. So I've been thinking about this a lot; what could be causing an intermittent vibration, or one that just varies in intensity. I'm getting the same thing, although it has only ever rode completely smooth once. I can't find a correlation between an environmental factor and the vibration intensity.. unless you consider having to gun it from a stop on an extremely bumpy road to get across traffic an environmental factor. After that I was immediately getting on the highway and when I got up to speed, the vibrations were so bad I thought my truck was going to fall apart. After about 10 minutes it finally mellowed out to "normal" vibrations. That time was the only time I've been able to attribute anything specific to a change in vibration. Anyways, back to the basic thought of what could cause a varying vibration: Out of round, or not, tires slipping on an out of round, or not, wheel. Obviously at least one of the two must be out of round to produce the 1st order vibration, and only as the high spot slips around wheel/tire. The "wheel hop frequency" AKA resonant frequency of the suspension changing. There's a few things to consider with this one:Wheel hop frequency is unavoidable. It's simply the natural resonant frequency of the suspension, it's not the root cause of the vibration itself. This resonant frequency changes depending on the spring constant and/or the weight of the vehicle. This could potentially explain why owners have noticed differences with full tanks vs empty ones, and loaded beds vs unloaded. It is (most of the time) a first harmonic of radial force that oscillates at the same frequency of the natural resonant frequency of the suspension (which is forever changing) that causes the vibration to occur So knowing this, we've opened ourselves back up to all of the other potential components that could cause a 1st order vibration that I went over in my last big post. Since the wheel hop frequency is always changing, anything producing a 1st order vibration might only cause a vibration as the wheel hop frequency changes to a matching frequency and could produce a varying intensity depending on the level of correlation. This could mean that even if every component of the wheel assembly was "perfectly" round (within tolerance) and the entire wheel assembly alone did not produce any noticeable vibration through to the cab, the frequency that it does produce could set off the resonant frequency of the suspension. This could be the vibration that we feel. So again, we're back to an on car balance or a dynamic balancer (Centramatics or BalanceMasters) being a promising fix in theory. They both reduce 1st order vibrations of all components at the same time dynamically. I'm also thinking that an add-a-leaf kit might be a simple way of changing the natural resonance of the suspension enough across its entire range that it wouldn't react to a 1st harmonic radial force from the wheel assembly at highway speeds. I don't know if that would cause it to react at a higher or lower speed though. Relatively cheap thing to try. Has anyone happened to do this already? Also, just another thing to think about; just like the wheel assembly, the driveshaft and all of it's related components can be out of round and/or out of balance. So just like balancing a tire can't fix a hub or rotor issue, balancing a driveshaft can't fix other components that might have an issue. That being said, there is also the same two solutions as the wheel assembly if replacing parts doesn't fix the issue. On car driveshaft balancing is a thing, although I think there's even less shops that do that then on car wheel balancing. And BalanceMasters also makes a dynamic driveshaft balancer using the same technology as their dynamic wheel balancers. Let's keep those brain juices flowing and figure out these vibration issues, at the end of the day there is a logical and scientific explanation, we just have to find it! The ideas I bring up may sound far fetched and are historically rare, but the logic is valid. I almost never speak off the top of my head in these posts and verify it all on the spot as I'm writing. Also, I think we're well past sticking with orthodox solutions/troubleshooting!
  5. That sounds exactly what I felt this morning. Lopey makes perfect sense. Certainly not as annoying as the highway vibration, and lowest priority on troubleshooting list. Wheels and tires are on the mod list, maybe I oughta just replace em and hope it fixes the problem as it has for you and others. That's the shop I was planning on taking the truck too just gotta find the time during the week to get over there.
  6. Haven't had any time to do any of my own diagnosis or get the on car balance, I put in 12 hours each day this weekend on a network move project for a client. Not fun. On my way to work this morning though I noticed a 50mph vibration that I hadn't ever felt before. Not sure if it was a one time deal, if I had just never noticed it before, or if it's a new recurring issue. It was a much slower vibration than the one at 75mph. I'll keep monitoring it. Ugh. I want to keep modding my truck, already have amp steps and a Corsa sport cat back, but I feel like there's no point if I can't get rid of this vibration. I rolled over some negative equity when I got the truck so I'm pretty much stuck in it anyway unless I want a different headache to deal with. If I can't fix the vibration I'll just have to deal with it and won't ever want to finish mods.
  7. Yea the shop I'm heading to trues the tires as well. Did they true them on the vehicle or off? This shop does it on the vehicle which might or might not be beneficial, but definitely introduces all kinds of other headaches down the road. I'm still on the fence about letting them true the tires. Unfortunately, I called right after my last post and they said they wouldn't be able to start working on my truck as late as I'd have got there in the afternoon. I wish I had known I was going to leave the office early today so I could have actually made an appointment. I'm not 100% sure that this will fix the issue, but I sure hope it does since it should be pretty easy to find the actual root cause if an on car balance does fix the issue, there's really only a handful of things it could be at that point. I've thought about the bearings as well, both front and rear. They could certainly be the root cause, or they could just be going bad as a result of some other bad component. I wouldn't be surprised if owners have actually found the culprit and fixed it only to not realize that they've already ruined their bearings beforehand which is continuing to give them vibration issues. I hope to be able to get my truck in sometime next week and I'll report results. Awhile back I read you experimenting with making your own body mounts, how's that going? The wheel and tire is spun at high speeds and shaved at its high spots to make the tire as round as possible.
  8. Thanks for sharing, I was actually hoping you'd respond after seeing some of the out of the box thinking you've been doing. I won't have time soon to measure runout or do any other sort of troubleshooting, but I definitely will eventually. I've got a lot of ideas to expand on, and a lot of possible theories I'd like to share to get everyone thinking. Hopefully I'll have some time to write it all out and share this week. To start, this afternoon I'm going to get an on car balance at one of the last shops here in town that do it, and apparently they do a stellar job. This will at least confirm it's something in the wheel assembly if my vibrations go away, and stay away. Then I can do some measuring later when I've got the chance.
  9. Time to start thinking outside the box since GM isn't and the same thing over and over is being tried by dealerships to no avail... I'm tired of reading about road force balances and driveshaft balance/replacements not fixing the problem. They've been trying the same thing for 3 years...what's the definition of insanity again? I've got the 65-80 mph vibration. It starts faintly at 65, peaks at 75 and fades away to 80 and is fairly smooth after that, although it isn't perfect. I can feel it mostly in the floor/seat, and only a little bit in the steering wheel. The jump seat armrest shakes pretty bad, it will visibly shake a drink but I don't think it would spill it. I have a 2016 2WD CC SLE Sierra with the OEM 20" wheels and tires. The vibration occurs regardless of what gear the truck is in, neutral included, and V4 mode doesn't affect it either. In theory this means that there should be no issue with any drivetrain component in front of the diff. EDIT: this is wrong out of context. Driveshaft and diff components could also be the source, but these would be 2nd order vibrations. Below, I determine that I have a 1st order vibration so that rules these components out.) I've used the VibSensor Android app to measure the frequency of the vibrations from 65-80 mph, meaning I've recorded multiple 60 second samples at various consistent speeds in that range. The tests all show a strong ~10-14Hz response depending on the speed. I've placed my phone on the armrest, floor, and dash with all similar results, the only change being the magnitude of the frequency. This frequency should point to a 1st order vibration. With all of that said, we should be looking at all things that could cause a first order vibration regardless of engine speed. My gut tells me that the problem lies somewhere in the wheel assembly, although a side bearing, cup, or shim could be the issue. Even still, with as elusive as this problem has been, it could be an out of balance radio knob To start diag of a 1st order vibration #PI1354C is actually the beginnings of a great bulletin, but for some reason GM stops diag and resolution after balancing the tires. Let's look at all the possible things that could cause a 1st order vibration below. Remember, runout can be radial or lateral. Tire balance Tire runout Wheel runout Tire uniformity/road force variation Incorrect mounting Rotor balance/runout (not warping) Rear axle shaft/"hub" runout Front hub runout Wheel stud runout Bearing runout I'm sure there's potentially others, but that at least covers a lot more than a road force balance. The most efficient way to diag all of this at home is to simply measure the runout and go from there, that way we're not just throwing parts and money at the problem. The Hunter GSP9700 will take care of the first 5 things to a certain extent. Placement of the tire on the wheel can help with runout to a point, and the machine will also alert the technician if the wheel wasn't mounted correctly, although this doesn't help when actually mounting on the car. I don't have the tools or time to measure runout of the other components, but I'm considering tackling it if no one here can easily do it. I realize we'll need many samples though. Once it has been confirmed that there isn't any excessive runout to any component, the other major vibration source is balance. The GSP9700 takes care of the wheels and tires which leaves the rotor as the only other thing that can be individually balanced (more on balancing the entire assembly as a whole later). Yes, there is such thing as balancing a rotor. No, I'm not talking about warping. Yes, I know that this is very uncommon. All reputable brake companies balance their rotors during manufacturing, however, I've come across many stories of OEM and even top aftermarket brake companies shipping extremely out of balance rotors. If GM's source has poor QA there could be many trucks with out of balance rotors. Find a machine shop that will check and balance your rotors. Finally, if you still have a vibration after confirming that runout is within tolerances, the tires and rotors are balanced, and road force variation has been corrected...balancing the entire assembly as a whole should be the next step. All of the "fixes" above are just band-aids. There is no such thing as a perfectly balanced and perfectly round component. So the natural frequency of any individually balanced or "rounded" (runout within tolerance) component can be exacerbated when installed with all of the other imperfect components that make up the assembly. What I mean is that stud runout for example can actually make it appear as if you have wheel/tire runout and you'll feel the same vibrations as if your wheel/tire actually had that runout itself. If bad enough, you'll feel the vibration. (and if you have multiple components that are bad enough it could be that the result would be a much higher order vibration and harder to diagnose) To attempt to put a band-aid on this, there's two popular options: on car balancing or a dynamic balancing solution like what Centramatic offers. But again, you have to hope that the amount of runout is small enough that the balance can compensate for it, or hopefully it's a true balance issue that is correctable. This entire theory also explains why there is such a wide variety of owners who have vibrations at different speeds and coming from different locations. smcgillis10 just recently fixed his vibration after replacing his drivers front hub assembly. My guess is he had bearing, stud, or hub runout that was bad enough any sort of balance never could fully compensate for it. This theory also requires that owners not read smcgillis10's solution and replace their drivers front hub assembly. That wouldn't do them any good if the out of spec component is in an assembly on any other other 3 wheels. Being that vibrations seem to be coming from the front or the rear, 2WD or 4WD, is another reason that I believe the issue must be coming from a wheel assembly component and not the driveshaft, transmission, pinion, u-joint, torque converter, or any of the other sources that are being looked at. This was mostly me putting together my thoughts on the issue so that I can begin my own troubleshooting on my truck, but I hope that some of you find it useful, or that it sparks some new thoughts here other than the same thing over and over for 600+ pages. Also, please let me know if any of my logic above isn't sound or if you can expand on any of my thoughts. Here are some links I referenced while putting together these thoughts: http://autoguide.com.vsassets.com/blog/wp-content/uploads/2016/03/PI1354C-GM-Truck-Vibration-Information-Bulletin-1.pdf http://www.barrystiretech.com/unifandbal.html https://www.youtube.com/user/WeberAuto/search?query=runout http://www.g-w.com/pdf/sampchap/9781605252131_ch16.pdf
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