A hydraulic system for controlling an impeller clutch in a torque converter

A hydraulic system 90 for supplying fluid to a torque converter 10 of an automatic transmission for a vehicle driven by a power source includes a hydraulic control system 92 producing line pressure LP and converter charge pressure CCL. A discharge line 112 communicates with an impeller clutch 28 and discharges hydraulic fluid from the torque converter 10 at a discharge pressure COUT similar to the converter charge pressure CCL thereby minimizing a pressure differential across the impeller clutch 28 tending to disengage the impeller clutch 28 and an oil cooler 94 to which fluid is supplied and from which cooled fluid returns to the control system 92.