Haven't driven my 4runner in a few weeks, but last time out was a long trip with 0 problems. Yesterday I took it out and when I got on the highway above 40mph or so, I started to hear a loud noise and feel a vibration.
As I slowed down, I could tell it was a repetitive thump noise that slowed down as the vehicle slowed down. Sounded like it was coming from under the rear seats or further back. It did not go away if I let off the gas, and didn't change in 2wd vs 4wd.
Video w/sound is below, seems pretty audible with volume up. I checked the driveshaft and wheels and don't see anything stuck there or obviously excessive play, etc. Would be grateful for any educated guesses on the source!
2007 4Runner Noise - YouTube