Hydraulic systems for shrinking landing gear shrink are described. An example apparatus includes a landing gear strut, a transfer cylinder, aircraft hydraulics, a pressure vessel, and a pressure-operated check valve. The landing gear strut has an outer cylinder and an inner cylinder movable relative to the outer cylinder between a first position and a second position. The landing gear strut has a first length when the inner cylinder is in the first position and a second length less than the first length when the inner cylinder is in the second position. The transfer cylinder exchanges hydraulic fluid with the landing gear strut. The aircraft hydraulics exchange hydraulic fluid with the transfer cylinder. The pressure vessel exchanges gas with the landing gear strut. The pressure-operated check valve controls an exchange of gas between the pressure vessel and the landing gear strut based on hydraulic fluid received from the aircraft hydraulics.