HYDRAULIC CONTROL SYSTEM FOR AUTOMATIC TRANSMISSION WITH SHOCKLESS 4-3 AND 4-2 SHIFTING

摘要

Disclosed herein is a hydraulic control system for an automatic transmission wherein a first friction unit (C3) is engaged in downshifting from the 4th speed ratio to the 3rd speed ratio and it is engaged in downshifting from the 4th speed ratio to the 2nd speed ratio. A first port (124g) of a 3-4 shift valve (24) communicates with the first friction unit (C3) and it is allowed to communicate with a second port (124h) when the 3-4 shift valve (22) assumes a downshift position thereof. The second port (124h) communicates via a first passage (454) with a fluid conduit (412) supplied with an actuating fluid pressure. A second passage (452) is provided which connects the second port (124h) to the fluid conduit (412). The first and second passages are provided with first and second orifice devices (662, 660), respectively. The second fluid passage (452) is blocked when a 2-3 shift valve (22) assumes a downshift position thereof.