Detent mechanism and transmission speed range selector valve

Claim 1

A transmission selector valve having a detent mechanism and operating in a pressurized hydraulic fluid system comprising, a valve housing defining a central opening, a spool reciprocably mounted in said central opening selectively defining at least three speed range positions including a high and a low position, resilient means normally biasing said spool to the low speed range position, said housing and spool defining a fluid pressure chamber receiving pressurized fluid from the hydraulic system for biasing said spool against the resilient means to the high speed range and holding said spool in the high speed range position when the valve spool is in the high speed range position, a plurality of grooves in said housing defining reverse, low and high detent stop positions of said valve spool, a detent mechanism including detent elements biased radially for selective reception in said grooves, throttling means in said hydraulic fluid system upstream from said selector valve for reducing pressure of hydraulic fluid supplied to said selector valve and the hydraulic fluid in said pressurizing chamber thereby releasing said spool allowing said resilient means of said valve to return said spool from the high speed range position to the low speed range position, said detent mechanism arresting movement of said valve spool and retaining said valve spool in the low speed range position responsive to the predetermined decrease in pressure in said pressurizing chamber.