How to move caterpillars of a tank?

I scripted the motion of the tank using wheelcolliders, but right now I don’t know how to move its caterpillars, I’d like to achieve the effect of tanks in Battlefield3, but I need help, please, could u give me a tip?

Try this link, hopefully it helps you: http://forum.unity3d.com/threads/67790-Animating-tank-treads
It even mentions the tanks in the Battlefield games in the last comment!!!

-Grady