2010 Ford Ranger, 2WD, 130k mileage, manual transmission.
Bought used in July 2017. Driven @ 8k miles/yr. Has been running very smoothly up to now.

For 2 weeks or so I've noticed an fluttering/rattle coming from under the hood. It sounds most like paper or something flapping around, or a muted rotating rattle.
At an idle- when I shift into any gear I hear the sounds. It goes away when I slip out of gear. It makes the noise when I drive, but it seems to reduce or go away at higher speeds past 40 MPH or so. It does not get louder at faster speeds or anything.

This morning I was stopped in-gear with the clutch pedal pressed down. The idle suddenly changed and it got a bit rougher, making the truck shudder a bit. Acceleration was not as smooth for the remaining 5 miles of my commute.

Transmission Pump? Torque Coverter?
Can I drive for another week, or should take it somewhere today?