Noise only happens under load in any forward gear. let off the gas and it goes away. ran it on the hoist at work and its definitely coming form the bellhousing area. removed the dust shield (no signs of contact). left it off, still made the noise. checked all the flexplate bolts. removed transmission. checked transmission pump. Everything checked out. Going to be putting the transmission back in tonight. looking to see if there is anything else I should check before putting it back together and living with it. (until something lets go and find out the hard way). thanks

https://www.youtube.com/watch?v=ci6uytmnUc0

Have you checked flexplate to crankshaft bots to see if they might be too long?

how long has it been making that noise?

when did it start? winter/summer?

What were you doing with the car when it started?

Pull the starter and look at the starter gear. See how far forward
the starter gear is shimmed. If you have another starter lying around compare both to see if there is any differences on how far forward the starter gear is. Could be the starter gear rubbing on the flywheel.
This happened to me a long time ago. Installed a rebuilt starter and I was getting that same rattling sound when driving. Turned out that the starter gear was shimmed forward too much causing the starter gear to rub on the flywheel.

Its a new block and new transmission housing. Basically just put it together using the internals I was using before.

I noticed it as soon as I started driving it.

The starter gear had plenty of clearance. I will check the gear a little better when I get home though. thanks

Its a mini starter that's very old

got another junkyard starter for $25. won't have it until tomorrow.

I can always use it for a spare.

Yep. thanks

Going to just live with the noise. When it breaks something I will report back on what it was.

How about crank to transmission runnout? Different trans housing could introduce mis-alignment. This is usually a manual trans issue (I have had it!) but can also affect autos... especially when parts are swapped and especially if the engine was line bored.

On an old power wagon (not put together by me) misalignment was enough to crack the clutch pressure plate, wipe engine main bearings and transmission input bearing. The symptom (besides eventually low oil pressure) was a light metallic noise from the bell housing caused (I believe) by the crack in the pressure plate moving.

Check the flex plate to converter measurement as well when you put the transmission back in. Could be putting to much rearward pressure on the crankshaft and in turn the thrust bearing specifically.

That is just the pump gear tabs moving in the slot of the vert.

The driving video is hard to determine the problem so is it more of a vibration?Did the vert have free play before bolting it to the flex plate?Did it pull up to the plate all the way?

Sorry the noise was #8 rod bearing.

Thanks for the update, Sorry for your findings,
but at least you found it before it let go and created more carnage.