Oldsmobile/Buick Repair: drivetrain growl, trannie, drivetrain

Question
I have a FWD 91 regal, 3.8L 4sp automatic with 122K.
  while driving I can hear a low pitched growl that starts at 15mph and is steady at all speeds.
The trans shift is good, no slipping at full power.
 Can this be a final drive problem? can this be fixed without changing the trannie? Does the engine/trannie need to be pulled?  thanks for your help

Answer
hi dax.well if rhe noise is comeing from one side or the other.then wheel bearing if comeing from trans then bearing internal.if you have to remove the trans then no eng does not have to come out ,check those wheel brngs real good.please take a min to rate my help  ty billymac