specs first: 2003 WRX, 150+k miles. still runs like a Timex, especially as i finally cleaned out that pesky P0171 code- tried everything (plugs, air filter, fuel filter) and ended up being the MAF sensor.

anyways. back to topic:

I'm getting a mechanical gear like noise while driving. it increases with speed and obviously does the opposite as well. doesn't matter if the clutch is engaged or not. usually starts at about above 20mph, and NOT when the car is cold.

levels: the angled dipstick right next to the turbo still registers on the high side (checked this morning when the car was cold as well as yesterday when hot) and the color of the fluid looks clean. engine oil is fine as well.

my R front wheel bearing is going, but the only evidence of that is a "clunk clunk clunk" at slow speed turns.

what else could it be?