An agricultural implement (10) has front and rear gangs (12, 13) of rotatable tillage tools arranged to follow each other along a line of travel. The front and rear gangs (12, 13) are mounted to a main frame (21F), which is mechanically linked to a hitch frame (22) by a self-leveling linkage system (32, 33). The linkage system (32, 33) includes a spring assembly (48) arranged to allow relative movement between the hitch frame (22) and the main frame (21F) when the implement (10) is in a lowered field working position. The linkage system (32, 33) has a pivoting cam (41) for changing the field working preload of the spring assembly (48) to provide multiple hitch operation modes. The linkage system (32, 33) is arranged to make the main frame (21F) level and the hitch frame (22) rigid relative to the main frame (21F) when the implement (10) is in a raised position. The linkage system (32, 33) also includes an adjustable stop device (43) that limits upward hitch movement to provide multiple rear gang hitch operation modes.
