Patent ID: 8435148

Claim:
A hydraulic control system for a transmission, the transmission having a hydraulically actuated device for engaging a Park mode and a Drive mode of operation, the transmission having a plurality of torque transmitting devices selectively engageable to provide at least one forward speed ratio and at least one reverse speed ratio when in the Drive mode of operation, the hydraulic control system comprising: a source for generating a pressurized hydraulic fluid; a range selection valve in downstream fluid communication with the source and moveable between at least a first position and a second position, wherein the pressurized hydraulic fluid is communicated to the hydraulically actuated device to engage the Drive mode when the range selection valve is in the second position, and wherein the pressurized hydraulic fluid is diverted from the hydraulically actuated device to engage the Park mode when the range selection valve is in the first position; a first valve in downstream fluid communication with the source and moveable between at least a first position and a second position; a second valve in downstream fluid communication with the first valve and moveable between at least a first position and a second position; at least one first clutch actuator in downstream fluid communication with the second valve and configured to engage one of the torque transmitting devices to provide the reverse speed ratio upon receipt of the pressurized hydraulic fluid; at least one second clutch actuator in downstream fluid communication with the second valve and configured to engage one of the torque transmitting devices to provide the forward speed ratio upon receipt of the pressurized hydraulic fluid; a first drive circuit communicating the pressurized hydraulic fluid from the first valve to the second clutch actuator and to the range selection valve to keep the range selection valve in the second position when the first valve is in the first position and the second valve is in the second position; a second drive circuit communicating the pressurized hydraulic fluid from the first valve to the second clutch actuator and to the range selection valve to keep the range selection valve in the second position when the first valve is in the second position and the second valve is in the first position; and a reverse circuit communicating the pressurized hydraulic fluid from the first valve to the first clutch actuator, communicating the pressurized hydraulic fluid from the first valve to the range selection valve to keep the range selection valve to the second position, and communicating the pressurized hydraulic fluid to the first valve to keep the first valve in the second position when the first valve is in the second position and the second valve is in the second position.