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.

 

[Doubeleive]

ya I think you could disconnect the alternator (wiring) and take it for a short run in the daytime and see if it's still present or not, cel will probably come on but nothing to worry about.

 

[xFuZzYx]

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

My alternator is around $600, it's a self exciting Ohio generator 300A alternator. I still sit at 14.8 voltage steadily going down the road. So with the alternator charging that strong, it couldn't be the culprit.

Edit: and just incase you didn't know, a Self exciting alternator means it runs without the harness being plugged in, it charges when being spun, with any signals from the harness.

 

[corvette744]

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!!!

Looks like you need to get it in the air-get it to the rpm that makes the noise at and Stethoscope the noise.I use a very long screw driver to locate the noise-you might be very suprised to what it is.Other wise your guessing and throwing parts at it.

 

[swathdiver]

I understand Fuzzy about the alternator but still rule it out as a culprit. I suspect it from my armchair here, nothing else can really make that kind of noise in the way that it does. Just rule it out.

 

[xFuZzYx]

I understand Fuzzy about the alternator but still rule it out as a culprit. I suspect it from my armchair here, nothing else can really make that kind of noise in the way that it does. Just rule it out.

How would I rule it out? I don't use the plug with this alternator already so how could I change anything about it to see?

 

[xFuZzYx]

So me and my friend were looking under the hood of my truck and we noticed this on the side of the air intake box:

The top was broken off, so we did this:

We covered it in duck tape to see if that stops the noise or not. I plan on replacing the part either way, I just want to see if this fixes it or not, I'll let you know after this test drive lol.

 

[Fless]

Air filter service gauge, aka filter minder?

 

[Doubeleive]

How would I rule it out? I don't use the plug with this alternator already so how could I change anything about it to see?

it has to be plugged in or wired up in some manner otherwise you would just have a dead battery, remove any wires and take a drive with no wires attached to the alternator, or remove the belt and get crafty with a drill to spin it it up

 

[xFuZzYx]

it has to be plugged in or wired up in some manner otherwise you would just have a dead battery, remove any wires and take a drive with no wires attached to the alternator, or remove the belt and get crafty with a drill to spin it it up

I have a 300A self exciting alt that doesn't use a plug. I also have 3 batteries with 130+ amp hours each, and I have 175 ft of 0 gauge ofc wire connecting the batteries together. I have 8 runs of wire total, 4 positive(+/hot) runs and 4 full length negative(-/ground) runs and 1 frame ground per battery. Tell me again how I can't run at alt without the plug attached...

 

[TeaSpoon]

Do you have an aftermarket air intake?


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