Help diagnosing strange ICE scraping noise (with video)

2011 Gen3 Prius iii in northern VT with ~105k miles. I first noticed this noise driving two days ago right after the temperatures dropped. It sounded to me like a chunk of frozen ice/snow stuck in the wheel well. However, when I pulled over to investigate, I couldn't find anything there.

After some further investigation, the noise happens whenever the engine is running at low RPM. It sounds really loud, like something getting scraped and dragged around.

• It doesn't happen at highway speeds, just slow speeds <25 or when stopped.
• It doesn't happen when running just on the electric motor.
• The drivetrain doesn't feel rough, it just sounds rough.
• When it's making the noise I can't feel it in the steering wheel and it doesn't feel like the car is shaking.
• With the hood open, the noise sounds like it's coming from somewhere much deeper than the engine.

I was hoping that with the temperature hitting 40 degrees today, whatever this potentially frozen thing was would melt and be gone, but it's still just as loud. See the video below and let me know if you have ANY idea what this is or if I should be majorly concerned.

 

@bisco about 105k

 

Good point! Yes, we can refer to the ICE as the engine

I will try to make a video with the hood open when my wife gets home (need someone to rev the engine). However, when I listened to the engine running it really doesn't sound like it's internal to the engine. it almost sounds like it's behind the engine and much lower in the car. Any ideas from the video?

 

does any part of the hybrid charging system spin when the engine is idling?

 

Yikes, that sounds bad. Transaxle fluid is checked from under the car, right?

If it was a damaged transaxle, wouldn't I feel it shaking while accelerating or idling?