Technical Crazy Chirping noise from bellhousing

I know this kind of breaks the rules, but i'm desperate. I've got a ford 5.0/AOD combo in a customer's '66 ford. When it gets good and hot (like after a short freeway trip), it develops this awful chirp coming out of the bell housing in park. you can kind of hear it when your'e coming down the fwy offramp but it goes away when you get to the bottom. during normal driving nothing, but once you put it in park, it fades in until its really loud, and it fades away when you put it in gear. it sounds like a real bad belt chirp, but it is not the belt. I guarantee it.

I've checked everything. it is not a belt, there is nothing rubbing, the flywheel and convertor bolts don't have any shiny spots, there are no shavings in the bellhousing. I am well convinced, as are the 8 other guys who have listened to it that it is in fact coming out of the bellhousing.

I've had the trans out twice. I've had the torque convertor opened up and took the pump out. the flywheel had no visible cracks.
This video isn't mine. its from like 4 years ago , but this is the exact same noise... The title says cracked flexplate, but there should be a question mark at the end. I found this on a bronco forum where the guy was trying to figure it out, but as many threads go ,there was no resolution posted.

this thing is driving me bats.
any help?

 

I'm just making guesses...but this caught my attention..."you can kind of hear it when your'e coming down the fwy offramp but it goes away when you get to the bottom."
That (to me) sounds like fluid level. Have you changed trans fluid and filter?
Then "fades in until its really loud, and it fades away when you put it in gear"...again...fluid?
I'm just guessing.

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For some reason the cracked flexplate isn't that uncommon......

 

Bump
.

 

How's the thrust on the crankshaft?

 

Flexplates are cheap enough to replace, Check the welds on the ring gear

 

You would have to take the flex plate off to really take a good look at it. Possibly the front pump is noisy?

 

Or a balance weight that came loose enough to call for attention?

 

Back in the previous century, when I started as a line mechanic, we had a fleet of big trucks that had automatic transmissions. We heard that “ squeak” for weeks! We checked everything! Couldn’t find the source. Finally weeks later, after driving these trucks eight hour a day, one quit pulling. Tore it down, the cracked fly wheel / flex plate finally totally spun out right at the crankshaft. The “ squeak “ would also change on these trucks at different times and different conditions. Just my experiences.







Bones

 

Kind of along the same lines . . . Have you checked the pick-up tube off the filter for cracks or a missing or damaged seal where it plugs into the trans? Maybe it's somehow picking up more air than fluid out of the sump. Maybe hook up a gauge and check the line pressure.

 

Is there a front pump bushing the convertor neck goes in? Lippy

 

my grandson's ot truck with a aod trans makes a noise like that but nowhere near that loud. hope you find it and post what it is.

 

OK.
So.
Whoever put the car together didn't set the PCV system up right. There was no breather in the system and the engine was trying to suck itself shut. As a result is was sucking air in through the rear main seal. Took the sealed oil cap off and the noise went away. So needless to say I installed a proper PCV system, drove the snot out of it, and its all good now.

Thanks for your input, and hope you don't ever have to spend the kind of time we did chasing this one!

 

Thanks for getting back, glad you fixed it.

 

wow

 

Crazy symptom for sure, nice sleuthing. I don't imagine the engine leaked any oil with that kind of vacuum inside it.

 

Well darn. I never would have guessed that as a source.

 

Nice... I would have had the transmission out and apart chasing it down...

 

Who would have guessed.
Thanks for getting back to us and sharing the details of your issue and the resolution.
Happy hot rodding.

 

Yep , something learned every day here. Thanks

 

I ran into something similar once myself....a 454 BBC with a PCV valve but just a rubber plug instead of a breather in the other valvecover. It had a set of those thin, stamped aluminum, gold anodized Moroso race valvecovers on it....vacuum would pull them down tight to the top of the rocker studs and make a rattle....but it was easy to spot as it permanently deformed the top of those thin covers, bowed them down even at rest. Idiot that put it together was a local repair garage "mechanic".
In the same engine, when the cam wouldn't just easily slide into the cam bearings, he took a big dead blow hammer to the front of it to get it in there...Comp 305H Magnum, and it had flat lobes on it when I saw it again 2 months later.

 

So nice but rare unfortunately when the fix is posted which helps others. Very good troubleshooting.

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My brain box needs a breather like that. Whenever I wrassle with a mechanical problem it creates a vacuum and I will start making funny noises, too.

 

Thanks for letting us know what you found.

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