...inserting a scope of some kind through the inspection cover?

Trying not to, but getting sucked into a neighbor's 01 Voyager automatic 114k diagnosis. I say it's cracked by the classic rolling marbles-in-a-can sound.

A shop told him converter or internal damage, not flex, $2600 rebuild if trans. It hits all gears fine, and the sound can only be heard at at/near idle. I pulled the inspection cov can't see anything. Trans fluid dirty but not burnt.

So is there another method to confirm? I don't trust the shop he uses.

Maybe remove the starter and use a mirror?

My thought too but the cracks are generally along the hub (JY pic), and if I could send something in the cover or starter, that'd be best?

Anyone do this, and have a specfic tool in mind?

What about 1 of those cameras used to look in the combustion chamber? Or the ones that plumbers use? Harbor freight sells them pretty cheap. Maybe they rent them at your local parts stores?