Gm Global Technolgoy Operations, Inc.

Kenneth J Micklash, Ii

Robert Charles Downs

James Kevin Mainquist

David Allen Blenc

An electro-hydraulic control system for an automatic transmission comprises a manual selector valve for operator direction of line pressure fluid to a drive passage when drive is selected or to a reverse passage when reverse is selected. A drive/reverse passage connects the drive passage and the reverse passage. A first check ball is disposed between the drive passage and the drive/reverse passage and a second check ball is disposed between the reverse passage and the drive/reverse passage wherein the check balls operate to pressurize the drive/reverse passage when either drive or reverse is selected. The system further includes six fluid operated selectively engageable friction devices, three friction device actuators each associated with one of the six friction devices, in parallel relation and electronically actuated to direct fluid from the drive passage to the respective friction device, and a two-friction device actuator operative to direct fluid from the drive/reverse passage to one of two friction devices. Three pressure-operated feed protection valves are disposed intermediate of two of the actuators and their two friction devices, which operate to prevent flow to the two downstream friction devices.

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Royal Oak, MI, United States of America

Kenneth J Micklash, Ii