High pitched whine between 35-40ish mph

https://www.youtube.com/shorts/4eZ0WxGyTdQ

This happens whether the truck is under acceleration, no input or braking but only when the speed is between 35-40ish mph. It doesn't matter what the engine RPM are (i.e., same speed different gear still has the sound).

It's definitely coming from the front and it's worse on the driver side than the passenger. I've confirmed it isn't rear diff as it's inaudible when the rear window is open.

I thought it might be a loose bolt but I went through and tightened everything up on the suspension.

Ideas?

 

Maybe the driver’s side mirror.

 

Do you have a cat stuck somewhere under the hood?

 

It's your defrost vent. Turn off any mode of defrost and see if it goes away or ceases to happen.

 

I finally got back around to troubleshooting this: not the defrost vent, not the drivers side mirror.

It's also only audible when the windows are down, so it's definitely coming from the front-end somewhere. I thought it might be the body line whistling where it was cut and lines up against the bumper so I taped up every join on every body panel and the bumper but the whine is still audible. Pulled the skid plates, torqued all the front-end, no change. Sat in neutral and revved it up to 2500 rpm or so and no sound.

It's audible moreso on the left than the right which is making me think some kind of suspension component.

Idler pulley is my next stop, I guess.

 

You sure you're not being pranked?



Good luck, I hope you find the source

 

That sounds like feedback, like the ring of a mic about to takeoff.

 

Hah I considered this. Maybe not exactly this but a zip tie or label or something near the intake.

but alas…

 

Thats as bad as one of our guys putting a hunk of cheese on the heater core of a friends older chevy truck during one winter.

 

I hope at least it was Limburger

 

So... it was not this. But it was kind of this.

This is the inside of a harmonica:




These are my ditch lights:



Spot the difference.

(It was my drivers side ditch light. It was at an extremely specific angle that caused the whine. A degree in either direction and the sound is gone. I can't even get it back in the spot that reproduced it.)

 

It was some name in the blue cheese family. This guy drove a few miles before blowing his lunch. Same guy another time, we mixed cayenne pepper in his red man chewing tobacco.