PG01
Supporting Member
2019 Yukon Xl Denali Issue
- Thread starter Mikef
- Start date
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Interesting, Seriously I have never noticed it before.
I worked automotive until 2009. Mostly GM repair shop as we were an ACDelco dealer. I do not recall seeing any GMT 800 or 900 trucks having anything but a standard 2” round crossover pipe from left to right underneath the bell housing in front of the trans pan. These were 4 spd and 6L80/90E transmissions (5.3, 6.0, & 6.2 liter V8’s).
Please understand I’m not denying your claim — Rather I’ve just never saw it until this 10Lxx transmission.
I believe the K2 trucks were not engineered to swallow the body of this new 10 spd. Rather they were probably working on the new truck platform (T2 I think?) when they were developing the 10 spd with FoMoCo. That would support the reason GM delayed the deployment of the 10LE for a couple years in their trucks vs Ford implementing them in the F150 right away, sans Camaro.
After being able to wrangle our Denali away from my wife for a few days commute this week, I’ve come to my own personal conclusion:
The “turbo” whistle I have goes away after a few blocks, or gone completely if I remote start the vehicle and let it warm for 5 minutes or so before driving.
This leads me to believe the “turbo whistle” is caused by exhaust passing the AFM 4 cyl flapper in the exhaust. I’m sure this valve is undersized a bit to allow for thermal expansion-so it doesn’t seize up when hot and expanded within the exhaust system. The narrowed crossover pipe creates a natural restriction in flow, therefore the exhaust is increased in velocity as it passes through the narrowed pipe (think Venturi effect).
This slightly higher velocity exhaust comes into contact with the cold AFM exhaust flapper and leaks past creating a whistle.
Because the exhaust system (post converter) is probably the same design as pre-10spd transmissions, it was not designed for - and allows some of this slightly higher velocity exhaust to pass by the AFM exhaust valve. This likely creates a whistle until the exhaust system warms and the AFM valve seals up as it reaches operational temp.
Just my humble thoughts... I expect a technical service bulletin (TSB) to show up sooner or later to address this. As it is an NVH (noise, vibration and harshness) customer concern.
If my wife noticed, and said it sounds like she is driving a bus, I’m sure many more complaints might be recorded.
Also soon soot and carbon buildup in the exhaust may mitigate the problem on its own after a few thousand miles, so it may be a moot point. (This would explain why the problem was not discovered during test driving by GM before this power train package was put into production)
- I’m thinking this may only effect these trucks in the first couple thousand miles.
Now that the ambient temp is finally above zero here in ND, and I have 1500 miles on my Denali, the “turbo sound” is only present for a minute or less, Vs the few minutes and extended time it was present before.
Sorry I rambled. Just thinking aloud through my keyboard.
Love the forum! Thanks for participating, it’s great to bounce problems and ideas off of other owners!
Best,
-Shawn
Sent from my iPhone using Tapatalk
Todd Gilkison
TYF Newbie
- Joined
- Nov 13, 2018
- Posts
- 4
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Todd Gilkison
TYF Newbie
- Joined
- Nov 13, 2018
- Posts
- 4
- Reaction score
- 0
I traded in 2015 for 2019 noticed Whistle right away. Mine is at steady acceleration or constant speed. Went back drove another Denali on the lot no whistle. They replaced the exhaust section that has the valve on with brand new no fix. They wired it open and it fixed the whistle but has a deep throaty sound. They said come in drive all the new ones find one that doesn’t whistle and we will change exhaust out. Gm only reported 3 issues when i bought mine what a joke for a $ 80k + vehicle. Now they want to weld valve open to fix!! I dislike Ford but they are looking better every day.
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I wanted to update. My turbo whine is when the engine is hot or cold. Mine happens during acceleration.
Took it to the dealer and he said it is no doubt the muffler. They had to order a new one. As soon as they change it I will let you guys know if it fixed it or not.
Took it to the dealer and he said it is no doubt the muffler. They had to order a new one. As soon as they change it I will let you guys know if it fixed it or not.
