A vibrating grid shaft assembly (10) for use in a screening plant having opposed screen frame sides (11), and which comprises: a shaft (12) which is intended to extend between the frame sides (11); stubshafts (13) projecting from each end of the shaft (12), and each adapted to be mounted in or on a respective screen frame side (11); a respective bearing (14) mounted on each stubshaft (13) and intended to be located inboard of the adjacent screen frame side (11), and defining a rotational axis (20) for the shaft (12); and, a respective load (15) mounted eccentrically with respect to the rotational axis (20) and incorporated within the shaft (12) adjacent to each stubshaft (13) and so as to be located inboard of the adjacent screen frame side (11).