Annoying grumbling/buzzing coming from rear end (..of the CAR, fools ;) )

[OhioSpyderman]

About a year ago I had the same problem and someone suggested replacing the inner bearings. I did so and the noise went away......about a month or so ago the noise began to return. Now its as bad (or maybe a bit worse).

The bearings I put in were OEM (purchased from the now defunct Rockville Mits).

Should I replace the bearings again? Rip the axles out again and grease the snot out of them? Replace the inners?

Any opinion is greatly appreciated....

I should add that the noise is barely audible until you reach 35-40 mph and at highway speeds is fairly annoying...also I JUST replaced the rear diff gear oil (about an hour ago) with no change....

Bob.