Whining noise from rear end or wheel bearing

I have a 2002 chevy camaro z28, V8 350, with posi rear, auto transmission and 70K miles. I have recently begun hearing a whining noise when driving over about 50 mph. It gets louder and higher in pitch as I increase speed. I also hear it as I decelerate all the way down to stopping. However, it does not change pitch nor is there any interruption as the gears change either upward or downward. I suspected the rear end, and had the fluid changed (it was the first time the rear end fluid had ever been changed as long as I owned it, about 45K miles). The whine is still there. While the rear end was open and they changed the gasket, I looked at the gears and they didn't appear to show any wear. There was a leak from the gasket apparent when they put it up on the lift.

So, is my problem in the rear end, the wheel bearing (the sound appears to come more from the left side than right side) or possibly the caliper is freezing up? Please help! I don't want to do more damage to the rear end if I can avoid it, if that is the problem. And if I do have a rear end problem is there a less expensive fix than replacing the entire rear end?