Soory for the re-post!My '94 940T is intermittently making a whining (sometimes whistling or grinding) noise while moving.It has done this on and off for at least two years.Today,it's back and worse than before.Cooler temps sometimes trigger it.The noise must be in the driveline-it only happens when car is moving;gear selection (and engine speed),including Neutral has no effect on it.It sounds like it is faster than wheel speed.I can't seem to locate the exact direction.Every time I even think of taking the car to a mechanic,the noise goes away!Symptoms point to diff,but why would they come and go like this?Anybody had this? sredwine 940T has 156K,V90 has 94K

I'd say driveshaft center bearing, relatively cheap, relatively easy fix. May involve a trip to the machine shop if you don't think you've got a steady enough hand with a hammer & punch. At 156k, I seriously doubt your differential is causing the noise, and your description of the symptoms matches what I've experienced with failing center bearings to a 'T'. Just mark the driveshaft halves in relation to each other, and to the flanges, before disassembly to ensure vibration-free driving.
-Chris