Noises from rear of car. Rear Diff?

[Staxta]

There seems to be a loud grinding sort of noise coming from the rear diff or thereabouts in my car whenever I'm driving in the lower RPM ranges. It can be heard around 1500-2000rpm, and is especially noticeable up hills. However, after 2000 rpm the noise seems to disappear.
Is this likely the rear-diff? Axles? Something else?

[Dead91silvia]

Could be a rear wheel bearing. It's not too uncommon in out cars...

[Staxta]

I'll try and get a video of the sound, but its similar to this http://www.youtube.com/watch?v=WXamZXPNTXA except only quieter, from the rear, and only at low RPM