Hydraulic control system for automatic transmission

A hydraulic control system for an automatic transmission including hydraulic servos for clutches and brakes to engage and disengage components in a transmission gear mechanism and having a forward clutch hydraulic servo and a brake hydraulic servo, and a manual valve, comprising:

• a modulator valve for adjusting line pressure to a predetermined modulator pressure;
• a control valve adapted to be shifted in response to signals based on positions of the manual valve and the vehicle running condition;
• a first oil path connected between said control valve and said manual valve as a line pressure oil path;
• said control valve including a first port connecting to the forward clutch hydraulic servo, a second port connected to the brake hydraulic servo for restraining movement of the vehicle, a third port connected to said line pressure first oil path, and a fourth port connected to said modulator valve so that, during a normal vehicle running condition, said control valve is arranged to connect said first and said third ports and to drain said second port, and during stopping and high speed coasting vehicle conditions, said control valve is arranged to connect said first and said fourth ports and to connect said second and third ports;
• a second oil path connected between said control valve and said brake hydraulic servo;
• and
• a shift valve situated in said second oil path, said shift valve not operating during a low speed vehicle condition, said shift valve being adapted to connect said second oil path when said shift valve shifts to a low speed position and to disconnect said oil path when said shift valve shifts to a high speed position.