Mysterious high pitched squeal from underneath under load

[DCSVT1]

Its not the whistle from your CAI is it? Some intakes are loud when sucking in air, especially at a certain rpm

No I don't t believe so. I've heard the sucking sound from day 1 with the CAI. This is much louder, more high pitched dog whistle. I'm going to look at the exhaust. Thinking that a tiny crack or gap might cause this but??
Ford had it for three days and couldn't figure it out. Said that it's still under warranty so " let's see what happens"....and they didn't rotate the tires. ( shaking head, deep sigh)

 

[Buzzard2]

I am now thinking a restriction in the exhaust system

 

[Buzzard2]

I guess my next step is to put it on a dyno and try to locate the source of the noise. Leaning toward a exhaust restriction or leak going to see the muffler guy hopefully Friday.

 

[Buzzard2]

My issue was the vacuum leak on the 4 WD hub losing vacuum and trying to engage. Had a crack in a Vacuum line and while accelerating vacuum would drop enough to allow the hub to partially engage.

 

[harknessbab]

Beside the vac leak, did anyone else find a different reason for the screeching? Have also taken to the dealership and they hear it but have no idea.

 

[FordTechOne]

Beside the vac leak, did anyone else find a different reason for the screeching? Have also taken to the dealership and they hear it but have no idea.

Purchase a mechanic’s stethoscope and start checking various front end accessory drive (FEAD) components by placing the tip on the stethoscope on each pulley retaining bolt. Compare the noise each one makes, it should be a smooth, consistent, low-pitched noise. If it sounds “gravely”, high pitched, or squeaky, the pulley bearing is the most likely culprit.

 

[harknessbab]

It only makes the sound at 3-4k rpm. Would i still be able to hear it at a idle?

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[FordTechOne]

It only makes the sound at 3-4k rpm. Would i still be able to hear it at a idle?

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If it’s a bad bearing, you should still be able to hear a difference when compared with the other bearings.