Strange noise

[Num12005]

I have a 05 ppv tahoe,it was a texas trooper truck.It has the hydroboost brake setup (if that matters).I have a humming noise from 30- 50mph.Its very noticeable,i have checked all accesories for bad bearings,thougt it was tge alternator but after rebuild,its the same.Any ideas?It almost sounds like a mechanical fan but i have electrics.The noise is def from engine bay.It comes in around 30mph and goes away at 60mph but then its a high pitch whine.While its the loudest i can change the sound with throttle,put it in neutral (while its doing it) and it goes away.Im stumped!Maybe its something with the hydroboost setup????

 

[Zigger21]

I have a 05 ppv tahoe,it was a texas trooper truck.It has the hydroboost brake setup (if that matters).I have a humming noise from 30- 50mph.Its very noticeable,i have checked all accesories for bad bearings,thougt it was tge alternator but after rebuild,its the same.Any ideas?It almost sounds like a mechanical fan but i have electrics.The noise is def from engine bay.It comes in around 30mph and goes away at 60mph but then its a high pitch whine.While its the loudest i can change the sound with throttle,put it in neutral (while its doing it) and it goes away.Im stumped!Maybe its something with the hydroboost setup????

when you slow down does it whine like a hmm hmm hmm

 

[Num12005]

yes ,but it is quiet while slowing down,it only makes tge noise under load.

 

[SnowDrifter]

Could be differential noise. How does the fluid look?

You mentioned it's quiet while gliding. What if you turn the wheel side to side as a sort of slalom?

Is the noise closer related to engine speed or wheel speed?

Do you have auto 4wd on? Or are you set in 2wd?

 

[Num12005]

its a 2wd,the rear end is a 3.73 posi and is quiet.Its definately coming from the front,under tge hood..It sounds like a differential whine but from the front. The power steering has a little tiny bit of whine,barely can hear it.The hyroboost setup is the only thing i can think of tgat it may be.Or water pump ,maybe idler pully?Ill post a vid

 

[02Lightning]

Pull the belt and drive it, see if it goes away. Be careful, it will get hot fast.

 

[Num12005]

Heres a vid,dont mind the shot,i was driving.You can hear it pretty good

 

[Num12005]

heres another

 

[CTUBS8732]

Sounds like howling.

 

[Mudsport96]