[storm9c1]

OK, now that we've eliminated accessories, we need to dig deeper. That's a weird sound, I was sure it was an accessory. Dang.

The next thing I would suggest is to crawl under and see if it gets louder at the bellhousing area. The flexplate could have debris caught in it. If it is louder there, pull off the inspection cover. See if you see anything rubbing. Or even see if the cover itself is bent and rubbing. Seen that happen multiple times. And flexplate noises tend to transmit through the crank and sound like they are coming from different areas.

If it's not that, then yes, it could be the timing chain. The thrust bearing could be shot and your crank could be walking. Or the cam could be walking. Or something could have worked its way under the timing cover. If you are sure it's not coming from the flexplate or transmission area, then I guess you'll have to pull the timing cover...