buzzing sound from driveline

[Sunbeam2]

1997 GC Limited 4x4 5.2 Motor automatic tranny
Just had both rear outer axle bearings replaced because one was bad and making a whoo whoo whoo noise. Now that the bearing Noise is gone it has been replaced by a sort of buzzing noise under there somewhere. Sometimes I can make the noise come and go for a little bit by accelerator movement but it is there most of the time. What can it be???????

[msdz]

Uhhh, I wonder if they replaced, changed, or even added gear oil to the differential? Check the fluid in the diff to see if it has enough in it.

[Sunbeam2]

It is full of fluid, I stood and watched as they put in 2 1/2 jugs of that special SYNTHETIC oil until it ran back out of the fill hole. What else can it be???????

[msdz]

I haven't the foggiest. Is it coming from the rear? Can you feel any vibrations? Only one thing pops in my head, the shims to align the pinion gear to the ring gear have got slack in them causing it to have the whine. But I kinda doubt that.

[Sunbeam2]

The only thing I am sure of is that it is coming from under the car, the faster I go the louder it gets