I have a strange problem, hopefully someone can help me out and save me some $$$...

Whenever I accelerate from 0 to say 38MPH.. I get this real real loud whirring/humming noise, to ME it sounds like the front end but I took it to Belle Tire and they said it MAY be the rear end differential..I replaced all the wheel bearings and that didn't do the trick.

I have goodyear eagle f1's that are nearly bald (i know I need new tires real bad).. but 4 new tires are about $900 and I was putting that off to just before winter (i drive it in the snow)..

I understand tire tread contributes to the noise, but this doesn't sound to be just my tires.. anyone have any ideas?