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.

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?

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.

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.

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".

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!

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...

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.....

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.

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!

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!

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.

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.

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.....

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.