I have a 2003 Outback w/ 75K, automatic transmission.  I bought it 
used- have had it for 5 months.  When I accelerate from a stop, there 
is a groaning noise coming from the rear (axle- tires) area.  It's a 
low noise- not high pitched whining. It last a second or two as I 
accelerate then goes away, and the the car runs fine otherwise. 
  
It happens when the wheel is straight or turned.  And it happens when I 
am forward gear or reverse. 
  
If I haven't driven the car for a day or two, then the noise is less 
apparent.  But then if I am starting and stopping a lot, it seems to 
get louder as the day goes on. 
  
Any idea what this might be?