Whistle from engine bay while accelating

[Cg86]

Hello all,

 

First let say thank you for anyone who can possibly help. I'm pretty frustrated as of right now, trying to run this down. 

 

2014 Sierra 1500 5.3L All Terrain 

125,000 miles

 

Noticed a whistle/whine coming from the engine bay, but only when under load (won't do it in park), and accelating (stops as soon as I let off the throttle). I first noticed it when I was towing, but now does it everyday. It seemed to go away after the engine got warm. However, it seems to now be staying regardless of temp. 

 

So far I've:

 

Changed all 3 belts, replaced the alternator, used a mechanics stethoscope with no luck. 

 

So my questions beyond what do you all think.

 1. Could this be coming from the PCV tube being worn?

2. Where else should I look for a vaccume leak? 

3. Literally anything else you may feel as pertinent, please let me know. 

 

Thanks Again,

 

CG

[shakenfake]

Just smoke test the intake and if you have a leak you will see it

[M1ck3y]

If you weren't so sure it's coming from the engine, I would guess potentially bearing related.

 

One generation before yours I had a 6spd that whined under throttle. Dealership opened up the trans and replaced the output shaft and associated bearings.

 

Whine was gone