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Wrench589

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  1. Wrench589
    Several vehicle specific attributes could make certain vehicles more prone to hydroplaning then others. Weight distribution, for example. Front vs rear vs all-wheel drive. Vehicle weight for the size of tires - some vehicle come with wide tires for weight and suck in rain and snow. I even wonder about wheel alignment and how that affect grip. Add all these to tire selection and/or tire condition, and results may be less then desirable.
  2. Wrench589
    I can see where this is going....I'll get this thing perfect about 2 weeks before we get rid of it. LOL!! Yes, it's is most likely the roof. Makes sense, after all. Especially when you see the flimsy little cross-bows they used to support it. I think it was Elripster that fabricated some custom spacers to wedge between the roof and the factory rook-rack bars, and he was very happy with the result. I always meant to try that, but since I don't have those roof rack bars I didn't. As as I said, ours is livable, so only so many hours in the day.... I never did pursue the rear axles....kind wish I had now. Marc, do you recall where they didn't run true?
  3. Wrench589
    Hey Shaun, interesting!! You don't happen to know if there is a TSB on his modification they made to yours, do you? Some photos? It seems weird that they told you they were adding them to the 2018 Tahoes, when there a people still finding the issue on 2018 and 2019 units; I wonder if they are only fixing the real problem units and biding their time till the 2020's are out.
  4. Wrench589
    EXSlider400, after 182 pages, the answer is NO, the problem has not been fixed. In fact, the root issue has not really been "discovered"; although I stronglt suspect GM knows what is going on. Likely some kind of body-beaming or other structural/body resonance. The result is a vehicle that is highly sensitive to any vibration sources that may be present, which seem to excite the problem. GM has been focused on getting the tires running a smooth as possible, since tires are always a may contributor, and has been able to keep most customers happy enough to carry on with life. As Marc noted, let the vehicle sit for a few days and the flat spots will drive the noise until the flat spots disappear. But any other rough road or vibrations will also cause it to be worse. A few people found improvement changing rear axles because they had one with excessive runout. GM also has a TSB to re-glue the roof skin to the cross-members, but to be honest, I didn't notice any improvement when I had that done. I did notice a big improvement when I put full winter tires on (softer) which were roadforce balanced to the 10lb GM spec for these "problem" trucks. I also saw a further improvement right after that with a front end wheel alignment. I also notice that in V4 mode, it is a bit more noisy in tha cabin, but not the full-on drone/buffeting. Based on the 182 pages, it also seems some vehicle are more prone to the issue then others. As well, some people are more sensitive then others. (My wife originally noticed it, but didn't really bother her. She didn't even say anything until I brought it up) The other thing I will say is the vehicle has 120,000km on it and it is not as sensitive as when it was new. But it's still hypersenstive to any vibs. compared to every other vehicle I've ever owned or have now. We have just learned to live with it. But the truth is, there is a flaw, GM has not fixed it, and they won't, now that there is anew design about to come out.
  5. Wrench589
    Actually, it's a known fact that the tires installed on most new cars are far superior to aftermarket replacements. It all about "tire uniformity", where the tire manufacturers test and grade each tire coming off the line. https://en.m.wikipedia.org/wiki/Tire_uniformity here is the multi-million dollar machine they use: So, the car manufacturers specify a minimum Uniformity Grade when they buy tires from the tire manufacturer, and only take the top quality tires. The rest....they end up at the tires shops and online retailers. That said, there would nothing stopping a carmaker from saving a few bucks and lowering the minimum quality level. And yes, this is very much the same topic and the Hunter Roadforce "balancing".
  6. Wrench589
    Been a while since I was on this forum. Thought I would check in. Can't say I'm surprised to see that this issue still exists. Many of us always said it seems to be a basic design issue, and looks like that is the case. Sad. My update is that after 78,000 km, I hardly notice the buffeting. And no, it's not that much m used to it.... it's still there. But not nearly as prevalent as it was when the truck was new. Only in certain road surfaces, or after the vehicle sits for several days and flat spots the tires, is it as bad as when new. Why the improvement? No idea. Only theory I have is the suspension and body bushings are getting worn/softer, and changing either stiffness (and hence natural frequencies) and/or the transmissibility of vibrations from the tires and drivetrain. in fact, the worst vibration in feel in then steering wheel is in V4 mode. Definitely generates more vibration. But, we've learned to live with it. We we still like the vehicle for its size for our family, and it looks great. But I will certainly never buy a GM product after this turd-mobile. GM screwed something up on this and decided not to come up with a true fix. Arse-wipes! i haven't tried Franks fix with the roof rack cross bars, but thought of it back in 2014 right after I bought the thing. I guess I couldn't bring myself to fork over $500 more to GM (or whatever they cost) to fix their screw up. On principle!
  7. Wrench589
    What you've described is the classic behaviour of a resonance. As discussed before, when the frequency of the moving parts matches the natural frequency of a component, the resulting vibration levels are amplified. All moving parts will have some residual unbalance. Normally this is not a big problem and the vehicle simply absorbs it for the most part. It seems that this generation of truck has a very sensitive natural frequency around 75 mph that gets excited by just about anything... tires, axles, driveshafts, etc. GM has focused on getting the tires perfect, but in the long run that is a lost cause ... tires will wear and go slightly out of balance and boom - problem is back. Until the root cause is addressed, these vehicles will always be flaky and shaky! My Yukon doesn't shake like the pickups, but I can feel each and every road imperfection in the steering wheel and seat. The vehicle doesn't seems to absorb any energy, but rather passes it all along to the driver. Of course, the suv's have the dreaded "booming" which is a whole other thread on this website! One thing I did notice on a recent 800 km trip through the mountains. When hard cornering (at least for a truck) all the vibration in the steering wheel seemed to go away. Something to ponder...
  8. Wrench589
    Very interesting. I had an opposite experience. Dealer did a routine wheel alignment and it seemed to reduce the buffeting drastically. So much for that meaning anything, if you had the opposite experience. For sure my transmission shifts funny sometimes. Like it's slipping between gears momentarily. Another fricken' problem with these junkers.....
  9. Wrench589
    Has anyone done the following tests: 1. Out the truck on stands and run it through the speeds, in both 2wd and 4wd, to see if the vibs are still there? This would eliminate tires once and for all. 2. Run the truck on a chassis dyno without the load, letting the dyno free-wheel, to see what running the tires on a perfect surface does compare to real-world roads. Again, seeing the real effect of tires vs the rest of the moving parts. Both these should elimante other factors, like fuel sloshing in the tank, aerodynamics, etc. Not sure how t safely run a vehicle at 80mph on stands, so just an academic discussion for now. Still, something to ponder.
  10. Wrench589
    GM definitely has the upper hand here. They can design to whatever tolerances and performance outcome they want, with three exceptions; first, safety standards are dictated by local laws in the various countries they sell vehicles in. These will force certain design requirements and resulting safety related performance. Second, any non-specific safety related performance to keep them out of court/jail. And third, performance outcomes that benefit them in the marketplace, against their competition, to help sell vehicles. Other than that, they are more or less free to define whatever standard they want. That said, defining ridiculously high acceptable vibration limits would certainly be questionable from a professional practice point of view. The engineers that develop these specs are typically bound by some kind of professional engineering practice standards to ensure they are acting responsibly and not just serving their master! At least, that's how engineering laws are in Canada. It would be very interesting to challenge GM specs via a complaint to the Engineering board that governs the engineers that defined it. One could review industry specs as well as what other companies use for specs as a basis of comparison. Of course, we would need to know who specified the levels within GM, which jurisdiction he or she is working in, and then file the complaint. So, somewhat an acedemic discussion as we could never find that information out, but fundamentally a valid aspect. I guess the complaint could go against GM themselves..... hmmm. That might get their attention!
  11. Wrench589
    True, the factory wheels are hub centric, so that hub OD can be checked with a finger dial. I checked mine and they are within a thou runout. BUT, I bought a set of aftermarket wheels for winter and the hub bore is larger, thus making them stud-centric! In my case, the aftermarket wheels seem to run a bit smoother, although could be the super-soft winter rubber doing that. Ive commented on this before, but in my opinion, GM's design isn't the best. They use typical conical nuts into conical holes that are usually used for a stud-centric design, but then use the hub-centric design as well. So, those diameters all have to be machined perfectly concentric, or they will "fight" each other. Is that a problem? Can't say for sure. I suspect it would induce some stresses into the wheel and the hub. Is that an issue? Well, I would say no, if there was no problems with the vehicle. Except.....hmmmm. Nah, these vehicles are perfect!
  12. Wrench589
    15lb...don't think so. It was Softail. Reported removing 18gm of material from the OD of the axle flange. That's 0.6 oz at that diameter. That would be an equivalent mass of about 1/4oz at the rim OD, where wheel weights are typically added to correct out of balance. 1/4oz is not a lot. If I recall correctly, when I was younger I worked at a service station and we sold tires and the smallest weight was 1/4oz. Certainly modern vehicles are more sensitive and balance tolerances are likely tighter now, but still, a 1/4oz is not much and a far cry from 15lb.
  13. Wrench589
    Regarding the axles, there was a lot of discussion on axles many months ago, when it was first discovered that the axle flanges were not running true. We discussed in great detail the radial runout of the Outside Diameter (OD) of the axle flange itself, and bottom line, from a weight-balance perspective it would be a small amount of unbalance. And, that surface is not part of the fitment for the wheel, so no effect there. The bigger effect would seem to be the "face runout" of the axle flange. Or the wobble side-to-side that some videos showed. With the wheel mounted, this magnifies to quite a bit of side-to-side wobble at the tread which would certainly be felt in the vehicle, especially when the two wheels on the same axle "get in sync" with each other. (When they are out of sync, they would literally cancel each out quite nicely!) no amount of road force balancing the tires off the vehicle could ever correct this. I suspect that what is happening is the in-sync/out-of-sync effect is playing tricks on everyone, thinking some other corrective action had a positive effect until they go back in sync and magically "the vibration returns". Back to the radial runout...the one thing that was never checked accurately was the bolt circle runout. Difficult to measure without a special jig or fixture. Would be interesting to see the result of that.
  14. Wrench589
    It's amazing that after all theses years of dealing with this issue, GM continues to waste time and money on a solution that does not correct the issue - Road Force Balancing. I mean, how daft must they be?? Time and time again, we see posts retelling the same story over and over again. It's epic, how stupid GM is. Obviously, the tires are not the problem. Obviously it's something else. Either that, or the entire tire industry is building tires that change their characteristics as you drive and if that is happening, there is no solution other than a vehicle that can mask the tires.....
  15. Wrench589
    Interesting. So, question for you.... Did the vibration stay gone after the wheel alignment right up to when you put the new tires on? Did you get a another wheel alignment done right after these new tires were put on? I noticed that after a wheel alignment on my Yukon, it was a totally different vehicle; smoother, lighter steering, and the buffeting at highway speed was pretty much gone.
  16. Wrench589
    You are 100% correct. GM pays a very small flat rate for all this warranty work, and depending on the dealership, the technician only gets paid when GM pays. So, out yourself in the tchnicians boots - are you going to spend 10 hrs diagnosing and funding the problem when GM/dealership is only going to pay you 1/2hr for a Roadforce balance? Nope. Are you going t spend the 5-6 hours to do a proper, full Roadforce balance when GM/dealership is only paying you 1/2hr flatware for Roadforce balance? Nope! When I had my Yukon in for the buffeting and they took the headliner out to re-glue the roof skin to the cross-braces (yea, GM glues their vehicles together! Can we all say "junk" together), I spoke to the technician doing the job. I said "man, this looks like a big job". He stopped, and in a very annoyed, pissed-off tone, said "GM pays flat rate 5 hr for the total job. Took me a day just to remove the headliner. I have to eat the rest." Sheepishly, I dropped the conversation. At the time, I was pretty choked that GM would treat the technicians this way. Talking about it now, stirs up same sentiment. BTW, that was early 2015... Over 2 years ago. And here we are, still getting no wher fixing these issues. Like davidtgibson said, GM is deflecting us until we get tired and give up (which I've pretty much done), all the while making their suppliers eat most of he cost. I'm sure the conversation between GM and their suppliers is simple- eat this or no more orders! Reminds me of someone's else's business practices.....
  17. Wrench589
    So, what is interesting about the levelling struts is that raising the front end and eliminating the factory rake would affect the front end geometry ever so slightly. I'm struggling for a theory on how that could be related to the shake/vibration, but interesting nonetheless. Must be something to it.
  18. Wrench589
    Got it. Thanks. I didn't realize that these new trucks use a strut like a car. Was thinking older style with separate shock and coil spring/a-arms.
  19. Wrench589
    Interesting. So, which of those last 3 steps do you think solved the 73-80 mph vibration; the Bilstein shocks, the level struts, or the alignment? BTW, pardon my ignorance, but what are "level struts"?
  20. Wrench589
    Ya, that's so funny when the sales staff says they never heard of it. Means they are flat out liars/in denial or so completely disconnected from the products they sell that they are what I always say they are....USELESS! I mean face it, when is the last time you went to look at a new vehicle and didn't know more that than the salesperson? I've had fun with it a couple of times, though. Been at a dealership with my Denali and a salesman would walk up and say how nice it is and "how do I like it". It's fun to watch them squirm as I launch into a 45 min explanation of all the issues and pull my smart phone out to show the websites with all these discussions! Try it...it's a total giggle. They can't wait to get away from you, all the while praying no other customer gets within earshot. LOL.
  21. Wrench589
    I sure hope that dealership isn't telling you that the wheel weights have anything to do with the Road Force measurements. If the are, then they are completely incompetent and will not be able to get the wheel/tires assemblies correct. Road Force and mass balancing are two completely different issues and high Road Force cannot be corrected with wheel weights. If the wheel/tire has high Road Force numbers, that is caused by wheel runout, tire runout, or tire non-uniformity or any combination of the three. (Non-uniformity is variation in the stiffness of the tire tread and/or sidewall around the circumference of the tire). The only chance to correct Road Force is to re-index the wheel to the tire to cancel out Runout in the wheel and the tire. But guess what,mthatbonly works if both the wheel and the tire have some runout. If only one has,my our are SCREWED - cannot fix the Road Force variation numbers. Need to replace the offending component. And , if the hig Road Force variation numbers are caused by tire non-uniformity, you might be able to counter-act some of it with reindexing to the wheel but again, only if the wheel,has some runout. If it s true, need a new tire! So , I think these dealers are screwing with us when they say they correctly the Road Force. I don't believe it. They are either full of crap or the technicians don't have a clue how to run the machine and are making it up smother don't look incompetent and get fired! And don't forget, GM is paying them flat rate to do this, so home much time do you think they really spend fine tuning these tires? Ha! Lastly, after the assembly has been Road Force checked and adjusted as best as possible, a separate step is to do the traditional dynamic weight balance. That's where wheel weights get used.
  22. Wrench589
    Actually, "frame beaming" is not about energy transfer. It's a lay-person term to describe the frame natural frequency being excited and the result is a resonant condition. The reality is, every frame is going to have a natural frequency. In fact, many may have multiple "modes" of natural frequency. Depending on the amount of inherent damping in the system and the available excitation forces/frequencies, the frame modes may or may not be excited into a resonance. This is quite obvious based on GM's TSB on frame beaming in previous generation trucks when the TSB notes that a significant amount of mass in the box will change the response of the "frame beaming". Simple vibration theory, where the natural frequency of a beam (the frame in this case) is a function of the stiffness and the mass. Changing the mass will change the natural frequency and hence "de-tune" the resonance. Simple. We use that principle all the time to de-tune machinery vibrations. Of course, who wants to haul around 1000 lb of sand bags in their 1/2-ton all the time! All that said, I believe several owners have reported that hauling some weight in the back of the truck really did not change things much. Tells me it's NOT frame beaming. Regarding vibration transmission, that's an entirely different topic.
  23. Wrench589
    Well, I doubt adding a u-bolt clamp will change the density of the material. The density is a physical property of a substance...so many lb/cubic in or cubic foot. Lead has a high density. Steel not so high. Air much, much less. And so on. Adding a clamp will not change the density. You need the change the molecular structure to change the density. The clamp will add a small amount of weight (mass). It may also increase the stiffness of the leaf spring assembly. And stiffness has a major role in vibration issues. In fact, I was thinking about some of the folks that added clamps to the leaf springs and improved the vibrations and the video pinion angle changing, and I'm wondering if adding the clamps to the leaf spring reduces the wind-up of the leaf springs and hence reduces the change in pinion angle? Interesting.....
  24. Wrench589
    Check out this video.... I had no idea there was so much wind-up of the axle housing with a leaf spring suspension! With that much angle change, how does any truck not vibrate like crazy? I would imagine the previous generation did the same thing...why no vibs there? Makes me wonder how import pinion angle really is on most vehicles.
  25. Wrench589
    Holy crap! The amount of "wobble" created at the tire from the face runout is shocking. No wonder there is some much vibration/shake felt in the cab. Still doesn't explain why this issue seems to come and go for some people but regardless, that is seriously defective. OK, has anyone gone into their dealer with and shown them the amount of runout measured on their axle flanges? In all the posts on this thread, I don't recall anyone saying that the dealer ever checked these measurements or any GM TSB focusing on the axle flanges. Obviously, that the first thing to check. Heck, I'm definitely going to check them on my Yukon first chance I get. Just a side note, not sure if the lateral runout on the face of the protruding "hub" means much,maps that surface doesn't really engage anything. BUT, it is indicative of any overall poorly machine part, as everything seems to have a ton of runout. Bottom line....those axles are JUNK!

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