Oil pressure control system for an automatic transmission system

摘要

An oil pressure control system for an automatic transmission system which includes a fluid torque converter, a transmission gear and friction engaging means adapted to be selectively supplied with line pressure for establishing a selected transmission engagement in said transmission gear, wherein speed shift valves which change over the supply of said line pressure to said friction engaging means are selectively supplied with a detent pressure generated by properly reducing said line pressure. The detent pressure acts to forcibly shift said speed shift valves toward a shift position for establishing a lower speed range in a manner that a speed shift point is biased to a higher speed range by an amount determined by the level of said detent pressure.