D250E Series II, D300E Series II, D350E Series II and D400E Series II Articulated Trucks Power Train Electronic Control System Caterpillar

The lockup clutch controls the direct drive electrically. When the ECM activates the lockup solenoid the lockup clutch in the torque converter mechanically connects the torque converter input shaft to the torque converter output shaft. This efficiently connects the power train to the engine. The ECM keeps the lockup clutch engaged as much as possible during normal operation. When the transmission shifts the lockup solenoid is deactivated for easier shifting. The ECM uses the transmission pressure in order to determine when the deactuation time begins and when the time ends. The machine is in torque converter drive when the lockup solenoid is deactivated. The transmission's reverse gear and the transmission's neutral gear are torque converter drive. First gear is torque converter drive on the low end and direct drive on the high end. The transmission gears (two through seven) are direct drive.