Hydraulic control system for an automatic transmission having a manual valve with a two gear default strategy
A hydraulic control system for a transmission includes a source of pressurized hydraulic fluid, a manual valve, and a default valve. A first set of solenoids are configured to selectively engage at least one of a plurality of shift actuators. The first set of solenoids is open when de-energized. A second set of solenoids is configured to selectively engage at least one of the plurality of actuators. The second set of solenoids is closed when de-energized. A low speed default gear is engaged when the first and second sets of solenoids are de-energized and the transmission is operating in a low speed gear ratio. A high speed default gear ratio is engaged when the first and second sets of solenoids are de-energized and the transmission is operating in a high speed gear ratio.
GM Global Technology Operations LLC
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Steven P.
Moorman