2015 YUKON NOISE IN CABIN

Elripster · November 4, 2015

Folks, I am the owner whose Burban had the issue and now doesn't. It has the Z71, towing, etc.. packages. Reattaching ALL roof bows and adding Dynamat did the trick. There is still a little bit of boominess at very low speeds over rough pavement which could likely be addressed by Dynamat on the surfaces below the rear windows but I don't notice it with the radio on. If you tap that area with your hand you can hear that frequency. If I get around to Dynamating my FJ60 and have some left over I might hit up the Burban but is a very low priority at this point. Most importantly my wife is happy with it now. As I was driving it home finally got to look at that excellent interior and think to myself "now this is a nice truck".

My GoPro videos are huge maximum resolution files and I don't have time/tools to parse it down for posting up. Besides, if you get a GoPro, you will just see the same thing for yourself. Or, have your dealer do what mine did. They drove my truck without the headliner to observe the sheet metal. It moved a lot. They did the remaining roof bow repair and re-tested without the headliner and it was far better. They consulted a hod rod shop nearby where they got the Dynamat suggestion and with GM's approval installed it. Again more improvement. Then they installed the headliner and it damped more noise as expected.

A comment was made about having the dealer do it right the first time and I think this is key. The first time they reattached the roof bow behind the sunroof. That cured the V4 drone but not the buffeting. At that point though, buffeting seemed to be more road surface generated rather than like a flag flapping in the breeze as it was initially. The second trip they nailed it with the roof repair described in the TSB which does say to attach ALL bows if they have come off of the roof.

The sheet metal is very thin on these vehicles and isn't likely to get thicker again given the CAFE regulations automakers must meet now and in the future. Teslas have had similar issues and they are over 100 grand. As another poster mentioned competing vehicles of this class have had similar issues. Clearly GM needs to make sure the roofs are properly secured as the sheet metal is too thin to self support. Maybe GM will decide to add some sound deadening material to the roof and rear window sides or maybe not. That's their call. However, I can say that there exists a solution to this particular problem.

If a truck has unbalanced components, that is really a different issue which will certainly be magnified by this problem but is not the cause, or solution to, this particular problem in my opinion. And, I am an engineer of EV vehicles which have even more NVH challenges due to the lack of a nice loud class 8 diesel engine to drown out the noise.

Frank

Edited November 5, 2015 by Elripster

16Denaliguy · November 4, 2015

I just walked into the house to post this as soon as I could. This is my road trip experience from today :

Cruise set at 64 mph and all alone on the highway with no vehicles in front of me. Radio was off and the buffeting was there annoying the hell out of me! Came up behind a line of cars and the buffeting STOPPED. It was immediate and very noticeable the difference in how the inside of the Denali was. Pretty much dead quiet with no air pressure problems or buffeting! Passed the 2 cars that were in front of me and the buffeting started again! So I pulled over for a few minutes and let the line of cars get in front me and I started out again at 64 mph and the buffeting along with the air pressure are there like always. Caught up to the cars in front and followed them for 5 or 6 miles and the buffeting disappears!!! It was enjoyable to ride in comfort again even for those few miles!

If someone else could try it and see what they come up with and experience the same thing, we may be on to something here.

Elripster · November 5, 2015

16Denaliguy, what you are seeing is typical of vortices generated and cancelled out by traffic. You might stand on the rear tire and push down the roof. If it flexes easily it is not supported by the bows. You should be able to feel them under the metal. Another test is to tap the roof with your hand. If it sounds like a drum and you can see the expanse vibrating, you definitely have a wide swath of unsupported sheet metal that needs to be addressed.

The repair turned my roof from a resonant drum sound when tapped to a dull thud which is how it should sound.

Frank

16Denaliguy · November 5, 2015

Hey thanks Frank for the info. Man, it was quiet for a few miles anyway!!

My 2016 Denali had the TSB to address the roof, roof bows and the leaking sunroof completed, the dealership said it was quite the mess underneath the headliner.

I just ordered Dyna Mat Extreme and will be installing it this coming week.

Elripster · November 5, 2015

I would still get up there and make sure the whole roof is bonded to the bows. There are three of them behind the larger one just behind the sunroof and you should be able to feel them attached to the roof. If the whole roof flexes freely you probably want to go back to the dealer and have them redo it.

Frank

boazEarl8 · November 5, 2015

I would still get up there and make sure the whole roof is bonded to the bows. There are three of them behind the larger one just behind the sunroof and you should be able to feel them attached to the roof. If the whole roof flexes freely you probably want to go back to the dealer and have them redo it.

Frank

Maybe a dumb question. How exactly do you feel them through the roof? Is it really that thin?

Elripster · November 5, 2015

Not a dumb question at all. The roof metal, and all of the truck's sheet metal is that thin. You might feel localized deflection between the bows but every foot or so the roof should be attached to something under it that is very hard to push in. One easy way to test this is to bang on the roof with your fist. If it sounds like a gong and you can see the roof surface vibrate the roof is essentially floating attached to nothing but at the edges. This will allow much buffeting.

I think that going into the dealer with a way for them to test this as well as observe it (drive the truck with the headliner removed) is a good way to get them really engaged in the solution. Many if not most of the techs are car guys that will enjoy really fixing this as opposed to just going through the motions. I banged on the roof to show them the vibrations and they got it immediately. I basically said that if it sounds the behaves the same after the repair it is almost certainly not fixed. The outcome was a roof that was tied down to the bows and well damped with Dynamat.

Frank

The Zip · November 5, 2015

In order to move on, somebody needs to try a different brand tire. If a different brand tire decreases the shaking/vibration, then the next thing to look at would be to try a different brand wheel. If trying those two things and the shaking/vibration decreases over a long period of time, then the tires and/or wheels could probably be eliminated as a cause.

There is a fella on the PU forum that went from 22" chrome chrome wheels with a vibration in his truck to 22" aluminum wheels with Bridgestone tires that ended with no vibration in his truck. Don't know the manufacturer for the tire on his chrome wheel. Yet to be seen if the no vibration last but he says it currently drives like glass.

FogDucker · November 5, 2015

There is a fella on the PU forum that went from 22" chrome chrome wheels with a vibration in his truck to 22" aluminum wheels with Bridgestone tires that ended with no vibration in his truck. Don't know the manufacturer for the tire on his chrome wheel. Yet to be seen if the no vibration last but he says it currently drives like glass.

I think he also mentioned that he never had the ~40mph vibration.

Two of my alu rims were reportedly off by quite a bit too. It did improve high speed smoothness, but had zero change to the booming/vibration.

It seems that we're all dealing with multiple issues with slightly different symptoms.

ajs800 · November 5, 2015

Folks, I am the owner whose Burban had the issue and now doesn't. It has the Z71, towing, etc.. packages. Reattaching ALL roof bows and adding Dynamat did the trick. There is still a little bit of boominess at very low speeds over rough pavement which could likely be addressed by Dynamat on the surfaces below the rear windows but I don't notice it with the radio on. If you tap that area with your hand you can hear that frequency. If I get around to Dynamating my FJ60 and have some left over I might hit up the Burban but is a very low priority at this point. Most importantly my wife is happy with it now. As I was driving it home finally got to look at that excellent interior and think to myself "now this is a nice truck".

My GoPro videos are huge maximum resolution files and I don't have time/tools to parse it down for posting up. Besides, if you get a GoPro, you will just see the same thing for yourself. Or, have your dealer do what mine did. They drove my truck without the headliner to observe the sheet metal. It moved a lot. They did the remaining roof bow repair and re-tested without the headliner and it was far better. They consulted a hod rod shop nearby where they got the Dynamat suggestion and with GM's approval installed it. Again more improvement. Then they installed the headliner and it damped more noise as expected.

A comment was made about having the dealer do it right the first time and I think this is key. The first time they reattached the roof bow behind the sunroof. That cured the V4 drone but not the buffeting. At that point though, buffeting seemed to be more road surface generated rather than like a flag flapping in the breeze as it was initially. The second trip they nailed it with the roof repair described in the TSB which does say to attach ALL bows if they have come off of the roof.

The sheet metal is very thin on these vehicles and isn't likely to get thicker again given the CAFE regulations automakers must meet now and in the future. Teslas have had similar issues and they are over 100 grand. As another poster mentioned competing vehicles of this class have had similar issues. Clearly GM needs to make sure the roofs are properly secured as the sheet metal is too thin to self support. Maybe GM will decide to add some sound deadening material to the roof and rear window sides or maybe not. That's their call. However, I can say that there exists a solution to this particular problem.

If a truck has unbalanced components, that is really a different issue which will certainly be magnified by this problem but is not the cause, or solution to, this particular problem in my opinion. And, I am an engineer of EV vehicles which have even more NVH challenges due to the lack of a nice loud class 8 diesel engine to drown out the noise.

Frank

Thank you, Frank for posting this info, again! I am taking all of this info with me tomorrow when meeting with field engineer at dealership. I'm hoping they'll follow suit with a the same solution. I wonder how tough it would be to pull down headliner and line roof with dynamat if they are reluctant to do this part?

16Danaliguy - Are you planning to do this yourself or take it to a shop?

The discussion seems ridiculous given these are new trucks and at the respected prices, but in my situation it's either unload it and take a loss or be patient and try to resolve the issue. I really like everything else about the yukon and as we all know there are very few options if people/cargo space are a priority.

Thanks again for posting a hopeful long-term fix for the well known buffeting issue.

Elripster · November 5, 2015

When it comes to resolving these issues often you have to let things run their course even if that means the dealer tries something the first time that you pretty much suspect won't fix it.

To anyone who is having a lot of vibration issues, you might at least make sure the roof is fastened properly per the simple tapping test I described. That issue will almost certainly amplify (booming and/buffeting depending on frequency) any vibrations. It might be that with this issue fixed your truck will no longer require unicorn grade carparts to ride smoothly.'

Frank

Cl Houn · November 5, 2015

Frank , that makes a lot of sense. Anything in the drive train out of spec that roof will pick up and vibrate seems like. Probably wouldn't notice some of these things if the roof didn't have this problem. anyone know the tsb numbers for the roof fix and rear end? Frank did you have the dealer put in the dynamat or did you do it yourself?

Edited November 5, 2015 by Cl Houn

Elripster · November 5, 2015

The Dynamat was the dealer's idea. They got permission from GM to do it on their own volition.

Frank

jasondenali15 · November 5, 2015

Rooting for you guys! It amazes me that a handful of dudes on a forum who never met are going to get this fixed before GM...

ajs800 · November 5, 2015

Rooting for you guys! It amazes me that a handful of dudes on a forum who never met are going to get this fixed before GM...

Ha. I was about to post the same thing this morning. I think additional attempts Frank's way will tell us a lot. Hopefully i will get that process started tomorrow after talking to dealer, GM, and field engineer.

It's a hilarious that I'll most likely have to connect my dealer to Frank's dealer, then to the field engineer, then to GM serv rep all before getting anywhere with the fix. This will all happen after GM customer service tells me they've never heard of such problems. so sad...