Shift Solenoid: Description and Operation

Solenoid valves perform virtually all control functions.

Valves are operated directly, without any intermediate element, meaning they must have very high output so that they can close against the sizeable flow areas and high line pressures.

Fast response is also required to meet the control requirements.

DEFAULT MODE
Two of the solenoids are normally-venting and two are normally-applying. This provides a default mode of operation in the event there is no electrical power.

^ In this mode the transmission provides 2nd gear in 'OD," "3," or "L" shift lever positions.

^ All other shift lever positions will function normally.

^ The choice of 2nd gear was made to provide adequate performance while still accommodating highway speeds.

CONSTRUCTION
These valves must be extremely durable and tolerant of normal dirt particles.

Hardened-steel poppet and ball valves are used.

The valves do not have close operating clearances.