PLEASE HELP!!! I can NOT figure out what this noise is...

[xFuZzYx]

I added a 2nd video, the sound is much louder in that video! Make sure you watch both!

My truck is a 2002 Tahoe LT 4x4 with 251,828 miles on it.

Here's what I can tell you about this noise:
-It is not speaker feedback. (Yes I have unhooked all of my amps and it's still there, even while the radio is on/off).
-It does not happen in neutral, only while driving.
-You can hear it from outside of the truck.
-It changes frequencies/pitch based on rpm's, not just speed.
-I can let off the gas at 70+ mph and the noise will go away until I start pressing on the gas pedal again.
-The colder it is outside the louder the noise is.
-My alternator is an aftermarket self exciting high output alternator, but still charges correctly and my voltage doesn't change based on the noise, so I feel like that rules the alternator out.
-If I lean my head back against the headrest it isn't as loud as when I'm leaning forwards.
-Sometimes it can take over an hour of driving before it starts happening.
-It can get so loud that you can't even talk over it.
-It still happens if I cut the AC on/off.
-It still happens if I cut the heat on/off.
-It didn't start until I had my lightbar installed and I had both my high beams and low beams replaced with led bulbs (I got all of that done at once) but I've in hooked all of these things and the noise is still there.

I'm stumped and the noise is so bad it makes me not even want to drive my truck.

PLEASE HELP!!!

 

[Scottydoggs]

could be a wicked vac leak. try spraying the intake manifold with carb cleaner where it meets the heads, tb and where the injectors install. gaskets tend to fail over time. spray engine running, if the idle jumps up you found the leak.

you can also spray the vac lines, they also like to break, plastic junk never lasts forever.

 

[Kelsda]

Does it still do this if you rev it up in park, take the belt (s) off run it for a short time to eliminate pulleys

 

[xFuZzYx]

Does it still do this if you rev it up in park, take the belt (s) off run it for a short time to eliminate pulleys

-It does not happen in neutral or park, only while driving.

 

[xFuZzYx]

could be a wicked vac leak. try spraying the intake manifold with carb cleaner where it meets the heads, tb and where the injectors install. gaskets tend to fail over time. spray engine running, if the idle jumps up you found the leak.

you can also spray the vac lines, they also like to break, plastic junk never lasts forever.

Any chance you could take a pic of where I need to spray the vac lines please?

 

[Scottydoggs]

Any chance you could take a pic of where I need to spray the vac lines please?

any of them you see, take the cover off the intake theres at least one under there. evap and pcv stuff.

 

[xFuZzYx]

could be a wicked vac leak. try spraying the intake manifold with carb cleaner where it meets the heads, tb and where the injectors install. gaskets tend to fail over time. spray engine running, if the idle jumps up you found the leak.

you can also spray the vac lines, they also like to break, plastic junk never lasts forever.

Does it still do this if you rev it up in park, take the belt (s) off run it for a short time to eliminate pulleys

Hey, I recorded a 2nd video that shows off the sound way better! Please watch this new video and see if that helps you identify what's causing this noise, thanks!

 

[Scottydoggs]

being it really seems speed related now, maybe its bad weather stripping on the door? shut the door on a dollar bill, see if you can slide it freely around the front and top of the door.

 

[xFuZzYx]

being it really seems speed related now, maybe its bad weather stripping on the door? shut the door on a dollar bill, see if you can slide it freely around the front and top of the door.

It's rpm dependant, not speed, it can go away while at high speeds if I'm not pressing on the pedal.

 

[swathdiver]

Fuel Pump maybe? If the sound if definitely under the hood, swap out that alternator.