Guessing its something with the differentials and/or tranny.
Noise is hard to explain but kinda sounds like back in the day when you would put a baseball card on your bicycle wheel, except not nearly as intense.
The sound varies by ground speed (not in pitch but frequency) and seems to be getting worse.
Just want to get an idea of how much to diagnose and repair. I know the fluids need to be flushed at the very least and hoping that's whats causing the noise, not something more involved.
car is a 2005 legacy 2.5gt with 5 speed manual. ~65,000 miles