Grinding noise...

[Jolbaru_LGT]

So... This might be impossible to answer, but again, there's a grinding noise coming from somewhere under my car under acceleration. It sounds like an aluminum can being ground up in the garbage disposal. Could also be a rusty old bearing somewhere as well. Now, I just looked at a diagram of the rear differential and there's quite a lot of bearings there... Yikes! There's a lot of places it could be coming from. 

I've almost ruled out the driveshaft itself, because it's only a few years old(Driveshaft Store) and when I try and move it, there's no play. But what else should I be looking for/looking at? I guess what I'm also trying to say, is there a painless way to inspect some things to figure out what's next? I can't imagine diving into the differential is easy, that replacing it or rebuilding it could be in order?

[Max Capacity]

If you can ride in the backseat while someone drives the car...you can hear a lot of things from back there. The other tip, drove next to a large concrete wall. Something like at the end of a shopping plaza with the window down. Sound will bounce off the wall.

[Scubaboo]

Start with the wheel bearings, easy enough to check.  Just lift with a jack and spin the wheels and grab the wheel and shake.