Moving Grid Repeating Animation

I'm a newcomer to After Effects so bear with me, as this is probably an easy effect to produce, but what would the best way to achieve this repeating grid floor effect be?

http://24.media.tumblr.com/50b7b9cbb51b51765d7d9ac5b26ab9e4/tumblr_mkg rqnnbLE1r048glo1_500.gif

I know how to actually make the grid with the Generate/Grid tool, and making a 3D layer out of it, but how can i actually get it to be a repeating animation?

Thanks!