strange noise from rear of fwd car

after a bumping a curb (sliding sideways), a fwd drive car makes a low-
pitch wallowing sound at the rear.  the tires were replaced and an
alignment was performed.  this resolved other issues, but the sound
persists.  the dealer did a precise alignment on top of the local
shop's alignment.  turning right makes the sound go off.  also, the
sound is not audible until 70mph or higher.  any idea what this could
be?  a jacked up wheel bearing or rotor wouldn't go quiet if the car
turned right.  do fwd cars have little boxes that act like non-posi
rear axles?  if they do, my guess is, that is messed up.