Universal room extension for expandable rooms

A mechanism to affect the coordinated movement of an expandable room in a recreational vehicle. The mechanism comprises a drive chain assembly and a lift assembly. The drive chain assembly has a pair of drive chains (upper and lower) that move generally vertically along vehicle structural members and then the chains are redirected for horizontal travel as the main hydraulic cylinders are actuated to extend or retract the expandable room. The movement of the upper and lower drive chains is synchronized by a rack-and-pinion mechanism. The lift assembly controls vertical movement of the room so that when the room is fully extended, the floor of the vehicle and the floor of the expandable room are substantially flush. The lift assembly comprises at least one lift cylinder for raising and lowering the room. The lift cylinder is vertically combined with the lower end of the structural member.