Control circuit for a transmission.

摘要

A control circuit for a hydraulically operated transmission for a vehicle, the transmission including a fluid line containing pressurised hydraulic fluid and which is connectable to an exhaust port for downshifting from one forward gear ratio to another forward gear ratio, the control circuit comprising a solenoid operated valve (318) positionable in the fluid line, the solenoid operated valve being biased to a normally closed position; a relay (510) connected to, and controlling the opening and closing of, the solenoid operated valve; and speed sensor means (508) monitoring the speed of the vehicle and providing a signal to the relay to open the solenoid operated valve when the speed of the vehicle is below a predetermined level. Prevents engagement of first gear ratio when vehicle speed is high enough to cause damage to the transmission.