weird whirring or metallic sound after drive car on highway for a while

[cumechanic]

hey guys,
I got a 2002 subaru legacy gt wagon 5sp manual and, whenever i drive the car on the highway for like 20+ minutes or so i start to hear this whirring sound no matter what gear i'm in (throw it in neutral, the sound is still there until i come to a stop). once the car warms up this sound is pretty constant at all driving speeds (doesnt sound "metallic" until over about 40mph). I can drive this car to/from work (about 6 miles one way) or to local bars and it's quiet, no whirring sound. I replaced the tranny fluid already, its topped off just fine, and NO it depressing the clutch pedal doesnt do anything. I cant decide if it's possibly a bearing (no play in the wheel but, bad bearings are not always diagnosed this way) or perhaps something in the tranny. the sound, when sitting in the car, sounds like its coming from the center of the car. only mods are a b&m short shifter. any ideas???

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[cumechanic]

alright so it was NOT the wheel bearings but the bearings in my transfer case had gone out. cost me$1100 to fix at a local shop (you have to drop the transmission for this job). So, if your subaru makes a whirring sound after driving it on the freeway for a while, your wheel bearings (when the car is lifted) do not appear to be worn (ie 12 o clock and 6 o clock shake test) and the sound comes up from your shifter compartment (and is made worse by lifting up the insulation- sound becomes very prominent) then you have bad bearings in your transfer case. wish i could have found a post like this for my legacy...