Abstract: A transmission throttle valve for use in a hydraulic control system of an automotive automatic power transmission, comprising a valve plunger movable with the accelerator pedal of an automotive vehicle and, a valve spool engaging the valve plunger through a spring urging the valve plunger and the valve spool to axially move in opposite directions relative to each other for producing a fluid pressure variable with the displacement of the accelerator pedal, wherein the valve spool is formed with an axial bore open at both ends and has the valve plunger slidably passed through the bore while the valve plunger is formed with a laterally enlarged axial portion forming a variable-volume space in which the fluid pressure developed by the transmission throttle valve is to be admitted to urge the valve plunger to axially move against the force of the spring so as to save the driver's effort for depressing the accelerator pedal.

Abstract: In a hydraulic control system of an automatic power transmission is provided a first-second gear shift valve which is to be acted upon through only one fluid inlet port by a signal fluid pressure representative of a manual first forward drive range selected at the manually operated gear shift lever, the port being used not only as the port to receive the signal fluid pressure but as a switching port so that the shift valve is conditioned to produce the first gear in the transmission mechanism in the presence of the signal fluid pressure.

Abstract: A governor is disclosed in which dust which may comprise steel powder, fine particles of sand and so on will be removed from a hydraulic working fluid by subjecting the working fluid to centrifugal force. A fluid passage for the working fluid is formed in a housing of the governor and a chamber communicates with the passage at the opening. The fluid passage has an opening located such that dust contained in working fluid will enter into the chamber through the opening while the housing is rotating. Within the chamber working fluid will be stagnant and dust sedimented.