Hydraulic control system with 4-2 timing arrangement for automatic transmission

摘要

Disclosed herein is a hydraulic control system for an automatic transmission wherein a first friction unit (C3) is engaged and a second friction unit (C2) is disengaged in downshifting from the 4th speed ratio to the 2nd speed ratio. An orifice device (660) is disposed in a fluid supply passage to a second port (124h) of a 3-4 shift valve (24) which is allowed to communicate with a first port (124g) communicating with the first friction unit (C3) when the 3-4 shift valve assumes a downshift position thereof. A timing valve (23) is arranged to provide a first bypass passage bypassing the orifice device when a fluid pressure in the second friction unit (C2) is lower than a predetermined value. A second bypass passage is provided to bypass the orifice device when the 2-3 shift valve (22) assumes an upshift position thereof.