Selectively engagable auxiliary leaf springs (38 or 142) for vertically supporting a vehicle chassis (32) on an axle assembly (22 or 102) in parallel with main suspension springs (34 or 114). In three of the disclosed embodiments, both ends (38b,38a) of the auxiliary leaf springs (38) are pivotally attached. In two other embodiments, one end (142a) of each auxiliary leaf spring (142) is pivotally attached and the other end (142b) is rigidly affixed in cantilever fashion. A manually operated hand crank (60) or ratchet mechanism (87) employed to drive a speed reducer actuator (62) to selectively enable or increase load supporting of the auxiliary leaf springs.