| 摘要 |
A hydraulic control system of an automatic transmission for an automotive vehicle includes a hydraulic pump, a pressure regulating valve, a torque converter, a converter clutch, first, second and third solenoid valves, first through eighth friction elements, second and third speed clutch valves, a band valve and a manual value. The pressure regulating valve varies a hydraulic pressure when shifting, and the converter clutch regulator valve actuates a damper clutch to improve transmission efficiency of the torque converter. The first, second and third solenoid valves supply or obstruct the supply of hydraulic pressure from the pressure regulating valve to a respective one of a first, second and third clutch shift valve to displace valve spools of a respective one of the first, second and third clutch shift valves. The second speed and third speed clutch shift valves as well as the fourth speed band valve, selectively supply hydraulic pressure to the friction elements to perform shifting. The second speed and third speed clutch shift valves as well as the fourth speed band valve are controlled by the solenoid valve and an overdrive unit valve.
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