System using vertical exhaust passage for maintaining primed condition of hydraulic circuits of an automatic transmission

A system for pressurizing and venting friction elements of an automatic transmission, comprising:

• a source of pressurized fluid;
• a sump having a fluid level;
• a first passage that is pressurized to produce reverse drive and vented to discontinue reverse drive;
• a second passage that is pressurized to produce forward drive and vented to discontinue forward drive;
• and
• a manual valve comprising
• a chamber;
• a first port connecting the chamber to the fluid pressure source;
• a second port connecting the chamber to the first passage;
• a third port connecting the chamber to the second passage;
• an exhaust port connecting the chamber to said exhaust passage means;
• a spool located in the chamber, the spool movable among various positions within the manual valve, each position associated with locating one or more of the lands of the spool to produce an hydraulic communication through the manual valve, the spool having a first land having a relatively small control area for slideably supporting the spool on a support surface and sealing the chamber, and mutually spaced larger lands for alternately connecting and disconnecting the first port, exhaust port, second port and third port;
• exhaust passage means extending vertically above the sump fluid level, for connecting the manual valve means and first and second passages to the sump.

A system for pressurizing and venting a friction element of an automatic transmission, comprising:

• a source of pressurized fluid;
• a sump having a fluid level;
• a friction element that is engaged and released in response to the pressurized and vented state of the friction element;
• and
• a manual valve comprising
• a chamber
• a first port connecting the chamber to the fluid pressure source;
• a second port connecting the chamber to the friction element;
• an exhaust port connecting the chamber to said exhaust passage means;
• a spool located in the chamber, moveable among various positions within the manual valve, each position associated with locating one or more of the lands of the spool to produce an hydraulic communication through the manual valve, the spool having a first land having a relatively small control area for slideably supporting the spool on a support surface and sealing the chamber, and mutually spaced larger lands for alternately connecting and disconnecting the first port, exhaust port and second port;
• said exhaust passage means extending vertically above the friction element and manual valve means, for connecting the manual valve means and friction element to the sump.