Any Ideas ??
Loud "whirring-sound/almost gear-like", Loud at start-up, calms-down a minute later, sound"imitates the shifting of tranny, though"not-loud" ,can still be heard. 166,000 Miles on rebuilt tranny, tranny works-fine, engine ,a quart every 500 miles,also runs-fine., Found and replaced 2 "vacuum-lines" split-open, right below 2 intakes, also this XC-90 is twin-turbo.
After replacing 'vacuumlines', sound "diminished quite a bit" , but returned after a few days. Car seems to run Fine, although " no power as before".
Now the 'Whirring-sound" seems to " be rattling/almost like falling-apart ".
Afraid to drive , fear'n a "tow-job"...or worse.
I'm pretty -sure I can "replace the part" , but would be nice, " if some-one could, point to the problem " or"a possible diagnosis".
Thanks All,

 

does it happen when the car is revved while standing still in park or neutral? or only when you're driving? if it happens when standing still you can probably find where the noise comes from with a mechanic stethescope or broom handle held to your ear.