Abstract: A small diameter cylinder 1a and a large diameter cylinder 1b connected to it are formed in a housing, and a stepped piston 8 comprising a large diameter part 8b and small diameter part 8a is inserted in these cylinders. A first pressure chamber 14a is formed on the small diameter cylinder side and a third pressure chamber 14c is formed on the large diameter cylinder side by the stepped piston 8, and an annular second pressure chamber 14b is formed on the outer circumference of the small diameter part of the stepped piston 8. An intermediate cylinder 10 is formed inside the stepped piston 8, and houses a piston 5 free to slide inside it which forms a fourth pressure chamber 14d. The fourth pressure chamber 14d is permanently connected to the third pressure chamber 14c. A rod 4 connected to the piston 5 passes through the stepped piston 8 in an axial direction. An end stopper 11 limiting the magnum stroke L1 of the piston 5 is provided, and sets the maximum stroke L2 of the stepped piston 8.

Abstract: A transmission operating apparatus includes a booster for increasing the transmission operating force, and a buffer device for suppressing rapid shift-changes caused by a change in the load due to the damper action of a hydraulic damper mechanism. A by-pass is incorporated into the buffer to permit working fluid to flow into damper chamber by-passing an orifice when necessary. A sealing member having a sealing portion is interposed in the by-pass to seal the by-pass under normal conditions but is resiliently deformed releasing the seal when the working fluid flows into the damper chamber.