Transmission control system with emergency operating mode

摘要

A control system for a vehicle powershift transmission includes a set of electrical connectors which in a normal mode, permit electrical power to be transmitted to microprocessor-controlled valve drivers for the transmission clutch control valves. These connectors may be swapped, in a limp-home mode, to permit power to be transmitted directly to the transmission clutch control valves. In both modes, a start-in-gear protection circuit including a pair of relays and switches coupled to the shift lever prevents the vehicle from being started up with a gear engaged. In the limp-home mode, a limp-home relay and a clutch disengaged switch prevents gear engagement until the operator has depressed and then released the clutch pedal, and the clutch pedal may be operated to modulate and control gear engagement.