Whenever I shake the back side of the lens near my ear, I hear a sound, like something is moving inside the lens. However, it is working properly when mounted. Is this normal?
I hear the faintest jiggle when I shake my lens (and I'm not shaking it very hard). I think my sound comes from the zoom ring moving slightly. I can feel some internal movement but I don't hear anything.
For what it's worth, I bought my lens on eBay, and it's suffered some shocks since I've owned it. Nothing major. I think it's in good shape.
It is normal to hear some clicking sound by shaking a lens, because of AF mechanism. Zoom lenses and VR make more noise because they are made of moving parts.