A filter press plate shifter assembly (21) provided with a shifter housing (22) having a tunnel-like center part which passes over the filter plates and housing parts positioned adjacent opposite side rails (14). Each side housing part mounts a pneumatic plate shifter (41) for permitting the endmost plate in the closed stack to be individually and sequentially shifted away from the stack into an open position when discharge of filtrate is desired. The shifter housing mounts a bumping device (61) which cooperates with the endmost plate in the stack to effect vertical bumping thereof relative to the support rails to assist in loosening sticky cake which adheres to the plate. The shifter housing also mounts an air-assist discharge mechanism (62) which includes a nozzle-bearing head assembly (80, 80') which moves vertically downwardly between the opposed faces of an open pair of adjacent plates for discharging airstreams downwardly against the plates to assist in removing the sticky cake from the plates. The overall operation of the shifter assembly is fully automated to permit each adjacent pair of plates in the closed stack to be opened, bumped and subjected to an air blast to cause discharge of sticky cake.