Whistle at part throttle

[keeper18]

I've got a brand new 2016 Sierra with the 5.3 in it. During light throttle applications I can hear a pronounce whistle. I've heard it on other new GMCs and Chevys too. I can't seem to find a definitive answer. Does anyone know what is causing this?

[14GMC22's]

Mine did the same thing until I wired open the "adaptive valve" aka flapper that is directly behind the muffler. I have better throttle response and no more annoying whistle/whine. It also sounds like a truck now at idle. Hope this helps

[15silver]

I have that, though sounds like its coming from up front. I thought it was the air being sucked past the butterfly at the intake when its only part open at light throttle. IE normal.

[14GMC22's]

Wire or bolt your valve open and give it a shot. I thought mine was an alternator whining when I first got it. Glad I read on here to open that valve up and it instantly went away

[MOhunter92]

Mine did the same thing until I wired open the "adaptive valve" aka flapper that is directly behind the muffler. I have better throttle response and no more annoying whistle/whine. It also sounds like a truck now at idle. Hope this helps

This exactly. My 15 did it and they had to replace the whole exhaust. It was gone after that, the valve was the culprit. My 16 didn't have the issue

 

 

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[JokerJ]

I have had the banks 2016 for a few weeks now and have noticed the whistle. If it's not hurting anything I might be able to live with it, but interesting how it's not noticeable during the test drive.

[Dnt]

Whistle? Hmmm I have never heard that on my 6.2 is it a 5.3 thing? Probably never be able to hear it now anyway since I have the dual exhaust installed, the pipes tend to drown out noises like the tranny whine etc. makes it much more enjoyable to drive. Vroooom