2015 YUKON NOISE IN CABIN

ajs800 · January 4, 2017

Thanks, Fog...we've chatted before and thanks for the info. Any idea if the dampers apply to the 5.3L? Also, are your sierra wheels oem or replicas? THanks!

FogDucker · January 4, 2017

Thanks, Fog...we've chatted before and thanks for the info. Any idea if the dampers apply to the 5.3L? Also, are your sierra wheels oem or replicas? THanks!

I'm not sure if the 5.3L exhaust is the same or if it applies. If the "boom" sounds the same, I would suspect that it does.

My Sierra AT wheels are OEM, also 20".

ajs800 · January 4, 2017

I'm not sure if the 5.3L exhaust is the same or if it applies. If the "boom" sounds the same, I would suspect that it does.

My Sierra AT wheels are OEM, also 20".

Thanks. Yeah, I'm suspecting the same regarding the "boom" sound.

Wrench589 · January 5, 2017

Correct. For me...

Booming (yes, over snow, gravel and other bumps) was fixed with exhaust dampers.

Buffeting was fixed by getting tires RF balanced to 12lbs or better.

Vibrating was fixed by replacing the rear axle.

I've put ~20,000 enjoyable kilometers on since all 3 were fixed. The buffeting started to creep back in fall and disappeared when I put my winter shoes on. I'm going to have the stock Continentals RF balanced (again) in the spring before I put them back on. If they're out of line, I'll get a set of Michelins or might just leave the Ko2's on all year as they've been great even though they're 15lbs heavier per tire than the Continentals.

Marc, when you say "replacing the rear axle" so you mean the two axles shafts, or the entire rear end assembly - housing, differential, gears, axles, etc.? It seems that over on the pickup forum, some have been replacing or truing the axles shafts with some success. Wondering what was done to yours.

SierraMyst · January 5, 2017

yep, low RF wheel balance is what will more than likely cure buffeting issue. We went with michelin premier ltx and made sure tire shop had low road force numbers and it fixed 90% of the buffeting. We shouldn't have to have 100% perfectly balanced tires to keep from having the issue but it is the way it is right now with these trucks.

We've always had the low speed booming and it never bothered my much but just recently it seems to be more noticeable and bothersome to me as well as passengers.

Leslie wasson Green - I see you have an SLT and had the new dampners and exhaust so does this fix apply to the 5.3L engine (models other than the Denali?)

The booming and buffeting are similar, but treated differently.

They are both related to the poor sheet metal on the trucks, hence why GM can't fix it unless they redesign the vehicle.

1) The buffeting is related to the upper sheet metal vibrating due to an imperfect ride. The stiff body mounts contribute to it making the vibrations in the metal harmonic in nature causing the steady buffeting sound at 40 mph and up. The made the body mounts on the 2017 slightly improved, but it didn't help enough to eliminate the issue.

The only fix for this is to isolate the roof sheet metal like some have done by placing inserts under the roof rack cross bars or by reducing the amount of harmonic vibrations into the truck from the wheels/tires through the body mounts to the sheet metal.

This fix has consisted of getting better tires and getting RFB number below 15 lbs.

2) The low speed booming is also a sheet metal issues, but specifically the sheet metal under the truck. Poor roads that have a lot of bumps cause the exhaust to jar up and down making the lower end sheet metal flex creating the boom. The booming is because the interior of the truck is extremely air tight, so you're getting a boom similar to a bass drum.

The fix for this is to reduce the jarring from the exhaust. Hence the dampers/ weights.

This is why the fix also works on 6.2L like FogDuckers and a 5.3L like Ozii's.

3) In addition to this, the 5.3L exhaust's flapper valve is also causing a harmonic vibration due to its location so tight to the underbody sheet metal.

In V4 mode, the flapper adjusts changing the pressure under the cab. That pressure and it's vibration also creates a buffeting sound.

Hence why there's a bulletin for the replacement of the exhaust on the 5.3L. but the buffeting will just return like on Leslie's Yukon.

The only real fix is to drive in M5 or M7 mode to shut off the V4 AFM. Or get a range device to shut off the AFM permanently.

The 6.2L, which is only in a Denali, comes with the Active Noise Cancellation, and the ANC reduces this V4 buffeting, hence why the exhaust replacement only applies to the 5.3L and the testing and repair of the ANC only applies to 6.2L.

There other vibrations on the trucks, but they are on a case by case basis, such as on FogDuckers rear axle.

But all in all, this is all caused by lighter weight sheet metal that flexes more tham usual, and was installed for the purposes of saving gas.

The real fix won't come until a design refresh.

And every Yukon and Suburban and Escalade has the same issues. On some it's not as bad and for others, it just doesn't bother them as much.

Edited January 5, 2017 by SierraMyst

ajs800 · January 5, 2017

Thank you for the detailed response!

I am fully aware of all of the buffeting issues and causes, however, i was not aware if the exhaust dampers/weights applying to the 5.3L. I am happy to hear it does as it seems ours has gotten worse and very bothersome recently. I've looked into many of the band-aids regarding the buffeting but so far the michelin premier tires have covered up most of it. I'd still like to attempt some of the other ideas but don't have the time or energy to deal with it.

SierraMyst · January 5, 2017

Thanks. Yeah, I'm suspecting the same regarding the "boom" sound.

It's the same. Ozii has a 5.3L fixed with dampers and FD has a 6.2L with the same fix.

ajs800 · January 5, 2017

THanks. Do you know the post # regarding the folks that attempted to fix buffeting by inserting object between roof and cross bars? I must have it missed this one. Ha

SierraMyst · January 5, 2017

THanks. Do you know the post # regarding the folks that attempted to fix buffeting by inserting object between roof and cross bars? I must have it missed this one. Ha

I'll have to go back a few pages, which isn't as easy on my phone. Let see...

FogDucker · January 5, 2017

The booming and buffeting are similar, but treated differently.

They are both related to the poor sheet metal on the trucks, hence why GM can't fix it unless the redesign the vehicle.

1) The buffeting is related to the upper sheet metal vibrating due to an imperfect ride. The stiff body mounts contribute to it making the vibrations in the metal harmonic in nature causing the steady buffeting sound at 40 mph and up.

The only fix for this is to isolate the roof sheet metal like some have done by placing inserts under the roof rack cross bars or by reducing the amount of harmonic vibrations into the truck through the body mounts and sheet metal.

This fix has consisted of getting better tires and getting RFB number below 15 lbs.

2) The low speed booming is also a sheet metal issues, but specifically the sheet metal under the truck. Poor roads that have a lot of bumps cause the exhaust to jar up and down making the lower end sheet metal boom. The booming is because the interior of the truck is extremely air tight, so your getting a boom similar to a bass drum.

The fix for this is to reduce the jarring from the exhaust. Hence the dampers/ weights.

Hence why this fix also works on 6.2L like FogDuckers and a 5.3L like Ozii's.

I spent many hours trying to isolate the buffeting and booming and last winter, I even drove around snow covered roads with all windows open and then only with the hatch glass open - the low speed over-bumps booming was still there. This should rule out the "air tight cabin" theory.

I also drove around for a while with Active Noise Cancellation disabled - it had no influence on the buffeting or booming.

My roof rails were installed after my 3 issues (booming, buffeting and vibrating) were fixed and I never tried wedging anything on the roof to limit movement.

I'm still not sold that it's the sheet metal, but this is outside of my area of expertise. There are some interesting companies that specialize in this sort of thing and could definitively identify the root cause at a cost. I would have expected the Suburban, with a longer roof, to exhibit a different buffeting sound than my shorty Yukon. The one that I drove for a week sounded exactly the same as mine at exactly the same speeds - 40mph and 70mph. Also, if it were sheet metal, I would have expected a higher percentage of vehicles (all?) to have this issue and that doesn't seem to be the case. I also would have expected to feel something inside the cabin at 40mph and 70mph if something was vibrating the roof. I crawled around the cabin and touched every part I could, including the metal floor boards, in every seating configuration while a neighbor drove around. I couldn't feel or hear anything as the buffeting occurred.

One way or another, there is an unwanted transfer happening that excites something. Maybe it is the roof. Stiff body mounts certainly seems plausible, but I don't think anyone has explored it a great deal. I think Wrench had them loosened/tightened with some influence, but not replaced. I'd also be curious to learn if they changed body mounts between the last model and the 2015+ model.

Marc, when you say "replacing the rear axle" so you mean the two axles shafts, or the entire rear end assembly - housing, differential, gears, axles, etc.? It seems that over on the pickup forum, some have been replacing or truing the axles shafts with some success. Wondering what was done to yours.

Brake rotor to brake rotor - the whole enchilada. It was shipped fully assembled in a wooden crate.

--

Marc

Edited January 5, 2017 by FogDucker

Elripster · January 5, 2017

I'll have to go back a few pages, which isn't as easy on my phone. Let see...

That was me. It works. I don't have a lot more to contribute in addition to what I already have. I still see people trying to do things that reduce the inputs to the chassis that excite the roof and get it buffeting. That's fine but trust those tires will wear, or your shocks will be extra cold one morning, or you will find a stretch of road with the right bump pattern.... and it will buffet again if you don't pin or otherwise hold the roof down. Dynamat on the underside of the roof also does wonders for the booming.

I dig my truck after wedging something between the roof and cargo rail + dynamat treatment.

Frank

Elripster · January 5, 2017

I'll have to go back a few pages, which isn't as easy on my phone. Let see...

That was me. It works. I don't have a lot more to contribute in addition to what I already have. I still see people trying to do things that reduce the inputs to the chassis that excite the roof and get it buffeting. That's fine but trust those tires will wear, or your shocks will be extra cold one morning, or you will find a stretch of road with the right bump pattern.... and it will buffet again if you don't pin or otherwise hold the roof down. Dynamat on the underside of the roof also does wonders for the booming.

I dig my truck after wedging something between the roof and cargo rail + dynamat treatment.

Frank

SierraMyst · January 5, 2017

That was me. It works. I don't have a lot more to contribute in addition to what I already have. I still see people trying to do things that reduce the inputs to the chassis that excite the roof and get it buffeting. That's fine but trust those tires will wear, or your shocks will be extra cold one morning, or you will find a stretch of road with the right bump pattern.... and it will buffet again if you don't pin or otherwise hold the roof down. Dynamat on the underside of the roof also does wonders for the booming.

I dig my truck after wedging something between the roof and cargo rail + dynamat treatment.

Frank

Could you share pictures?

SierraMyst · January 5, 2017

I posted pictures back in August. You can find them here.

I'm happy to see this solution work for others!

FD,

Could you confirm the location of the the 5 dampers?

From your pictures I see 2 before the cat, 1 after the cat, and 1 after the resonator before the spare tire.

Where's the 5th?

FogDucker · January 5, 2017

FD,

Could you confirm the location of the the 5 dampers?

From your pictures I see 2 before the cat, 1 after the cat, and 1 after the resonator before the spare tire.

Where's the 5th?

Oh sure, ask the Canadian to crawl under his truck in January! ;) I will be rolling through the Virginias in a month or two on my way to Florida - got a lift?

Next chance I get, I'll take a closer look and will snap some more pictures.

--

Marc