So, I have this annoying as hell squeal from what sounds like the rear of the engine. It's loudest from under the car around the bell housing. Though I know just because is sounds loudest in one area doesn't mean that's where the noise is coming from. It just started, noticed it once I got to work one day.

From what I've noticed I observed the following: 1- there's no noise cold. I can start the engine, let it idle all day and won't make the noise. No hint of a mechanical issue. I have to let coolant temps get to 185°+, then hold over 2k rpm for several minutes for the noise to start. Comes on real gradual until you can't stand it. Takes a while though. 2- noise doesn't change at all while pushing the clutch in or out. 3- noise is still present with the drive belt off. 4- unplugging all vacuum lines doesn't change anything. Sprayed brake clean all around the intake with no change. 5- sprayed front crank seal, water pump seals, rear main with WD-40 with no change. 6- noise seems to go away with load, can't confirm that. 7- tightened all exhaust with no change.

So far I have removed the valve covers and intake with no obvious signs of issues. Oil pump drive feels fine. I cut the oil filter apart and found nothing abnormal. I was going to pull the pan and inspect the rod/main bearings, but I'm not convinced it's a mechanical issue.

For what it's worth:
About 3k miles since rebuild.
383 eagle crank/6" rods/ icon forged pistons.
Lunati billet cam/all comp magnum valvetrain.
Lt4 heads/intake
Long tubes/Corsa

See link to youtube video of noise. Thanks in advance for any ideas as I'm at a dead end and feel like pulling the pan would be a waist of time.
https://youtu.be/KSBA-nO4hGs

 

It seems to be in sync with the lettering on the belt. Did you check the alignment of the pullys or give the belt a shot of belt dressing or WD40 to see if it helps?

 

That "squeal" sounds awfully familiar to me, like few minutes before (when) the serpentine belt tensioner on my Taurus came loose.

 

some valve or vacuum hose that spits air?

 

Thanks for the suggestions. Yes sprayed and removed belt with no change.

And don't feel it's a vacuum leak as unplugging all vacuum lines didn't make a difference either. Also sprayed all around intake with brake clean with no change.

I'm honestly lost...

 

It’s definitely rhythmic. Pull the filter and cut it apart and inspect it if you feel it’s deeper.

You could also get a stethoscope and see if you can narrow it down.

 

Yep cut the filter and didn't see anything abnormal.

I currently have the intake and valve covers off and don't see anything. I really don't want to pull the pan but I'm lost at this point. Would like to think if it was a bad bearing or lifter it would of shown in the filter.

 

That’s what I was thinking but saying it is bad luck.

If you have to pull the pan just tap on each cap with a small ball peen hammer. Without pulling it apart there will be a noticeable hollowish (more of a dead clunk) sound to whichever cap or journal is bad.
It saves time instead of pulling every cap or journal off. If there is no noticeable difference in sound it’s just the cost and effort of a pan gasket.