Slide-out operating mechanism for expandable vehicle room

A slide-out system for a recreational vehicle has a slide block (42) that is form fit with a sliding connection to a track (48) so as to vertically and laterally support a slide-out room relative to the stationary portion of the vehicle. The room is driven in and out by a rack (52) and pinion (60) drive and a synchronizing screw is provided at at least one end of the drive shaft so that two spaced apart slide-out units can be synchronized relative to one another and to ease disassembly of the shafts and motor drive unit.