Loud Squeal coming from front area of TH400 w/LS

Supersport1963

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Joined
Sep 4, 2024
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16
Just swapped in a 5.3 LS into my CJ7. I bought a used TH400 that I bolted up behind it. I had to use the .4 adapter on the end of the crank to get the proper flexplate spacing but everything went together easy.
Fast forward to finally getting it running. Everything works perfectly, except, when it has been running for probably 10 minutes, it starts to make a loud squeal from the front converter area it seems. Sounds very similar to a loose belt, almost identical. It stays when in any gear or neutral but I can get it to go away by revving up the rpm’s a little or even just putting a bit of load on the motor. It’s most present at idle of when lightly loaded.
I hesitate to think it is mechanical as I can make it go away with revving up a little or fluctuating the gas of bringing the rpm’s up a bit.
There are a lot of articles referencing this maybe being related to cheap filters? I pulled the pan and replaced with a brass screen filter and new orings and pickup tube and it didn’t make a difference.
I am a bit stumped. Throw out some ideas if you have them.
 
Few pictures for the hell of it.
 

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Interesting update. Got Jeep warmed up and sure enough, 10 minutes in it started to “squeal”. I crawled under and had a buddy turn the key off. After the flexplate and torque converter stopped spinning, the squeal continued on for a couple of seconds. You could hear the squeal die off if that makes sense but the flexplate and torque converter were definitely well stopped and the squeal continued.
Is there anything inside the torque converter or trans that could still me turning, due to inertia, for a few seconds after the crank and torque converter stopped? Only other thing I can think of is there Air pressure building up somewhere that is creating a whistle? It sounds very similar to a belt squealing.
I think rotation stopping would rule out a bushing or bearing in front of the trans
 
Check PCV system on the engine. I have seen a squealing belt complaint turn into a bad PCV valve before.
 
TC should be seated all the way, I measured the spacing and it was just on the edge of tolerance and so I spaced it out with some washers and it is well within tolerance.
PCV is where I am going next.
With the “squeal” continuing on after rotation has stopped, if feels like it has to be built up pressure or a pressure leak that is causing this. I don’t understand how the pump works well enough on the trans to determine if/how it could make that noise.
 
To come back to this and update it, it turns out that the clean air vent on the front passenger side valve cover was blocked and not allowing air to come into the motor. The result is apparently there was a significant vacuum created inside the motor and causing the piercing whistling noise.
I got the air port open and connected back to the port behind the throttle body and it runs great.
 
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