| 摘要 |
A hydraulic control system is provided for an automatic automotive vehicle transmission of the type including a gear changing unit, such as a planetary gear unit, having brakes and clutches controlled by hydraulically operated servo units, and including hydraulic torque transmitting means, such as a torque converter, coupling the gear changing unit to the vehicle engine. The hydraulic control system includes a cutoff valve hydraulically associated with a pressure regulator valve and other related control valves. The cutoff valve operates as a line pressure regulator when the pressure regulator valve is rendered ineffective in set positions of a manual speed selector valve. In particular, the cutoff valve becomes effective, with the pressure regulator valve becoming ineffective, when the speed selector valve is moved into the "reverse" position. The cutoff valve provides a higher control pressure for the servo units, during gear shifting in the reverse range, than the control pressure available for the servo units during gear shifting in the ordinary forward driving range.
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