Kinetico Quad 40 40 Problems...

I have a Kinetico Quad 40-40 which has worked well in the past but now is not doing so hot. It is not using salt so I think it is not cycling, however if I turn the screw to force it into action, it does the brine rinse and backwash and then stops itself. I took the head off and the gear sets spin well but I don't really know that much about it. Read something about the gear being sheared off but haven't looked into it again. Also I would like to replace the media. I have done this on another type of setup, but not this little Kinetico. Any help would be greatly appreciated.