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Basic diagram for the power train systems | |
The power train is made up of three basic systems. The following systems are the three systems:
- Power Train Electronic Control Module
- Torque Converter
- Planetary and Transmission
The three basic systems have a hydraulic connection, an electrical connection, a magnetic connection, or a mechanical connection.
Power is supplied from the engine to the torque converter. Power goes from the torque converter to the speed increaser and then to the planetary transmission. If the transmission is in gear, power flows from the transmission to the output shaft.
The operation of the power train begins at the Power Train Electronic Control Module (Power Train ECM). The Power Train ECM receives information from the selected speed of operation through sensors in the electrical system. The Power Train ECM uses the information from sensors in the electrical system to control the torque converter and the transmission hydraulic system.
The rotating housing of the torque converter is fastened directly to the engine flywheel. The torque converter has a lockup clutch for direct drive and a one-way clutch for torque converter drive. During torque converter drive, the torque converter drives the transmission hydraulically. During direct drive, there is a direct connection between the engine flywheel and the transmission.
The Power Train ECM will activate the lockup clutch solenoid when direct drive is necessary. When the lockup clutch solenoid is activated, the lockup clutch is hydraulically engaged. The lockup clutch becomes a direct connection between the rotating housing and the output shaft of the torque converter. The full power from the engine flywheel is transmitted through the torque converter when the torque converter is in direct drive.
The output shaft of the torque converter is connected to the speed increaser and planetary transmission.
The Power Train ECM will activate the upshift solenoid or the downshift solenoid when shifts are needed. The upshift solenoid and the downshift solenoid hydraulically activate the rotary actuator of the transmission. Movement of the rotary actuator mechanically selects the position of the rotary selector spool. The flow through the rotary selector spool hydraulically activates the correct valves in the pressure control valve. These valves engage the correct transmission clutches. The transmission clutches mechanically connect the transmission input shaft to the output shaft.
When the rotary selector spool is in the position to engage the correct transmission clutches, the transmission gear switch will electronically signal the Power Train ECM that the shift is complete. The Power Train ECM will stop energizing the upshift solenoid or the downshift solenoid.
When the output shaft of the transmission is rotating, the transmission output speed sensor will provide an electrical signal to the Power Train ECM. The signal is proportional to the transmission output shaft speed. The transmission will not drive the output shaft unless power is flowing through the torque converter.
The transmission has eight forward speeds. If the transmission is equipped with the warm-up mode feature, the transmission will have seven forward speeds. The selection of the desired speed is done manually.
When the transmission is in any forward gear, the torque converter will be in either torque converter drive or direct drive. The selection is dependent on engine speed and converter speed ratio. The torque converter will be in torque converter drive for a short time during transmission shifts providing smoother engagement of the transmission clutches.
The torque converter hydraulic system uses oil that is also common with the transmission hydraulic system. These systems use the same section of the transmission case.
Some components in the torque converter hydraulic system include a torque converter inlet relief valve, torque converter outlet relief valve, gear pump, torque converter hydraulic filter and a torque converter lockup clutch valve.
Pressurized oil that will engage the lockup clutch comes from the transmission section of the gear pump to the transmission oil filter. Oil flows through the transmission oil filter. Some oil is sent to the selector control valve and some of the oil will be sent to the torque converter lockup clutch valve. When the torque converter lockup clutch valve gets a pressure signal from the lockup solenoid, pump oil from the gear pump will be sent through the torque converter lockup clutch valve. This oil engages the torque converter lockup clutch.
Oil from the torque converter charge pump section goes through the torque converter hydraulic filter. The oil goes past the normally closed torque converter inlet bypass valve and into the torque converter. Oil exits the torque converter and flows by the torque converter outlet relief valve. The oil then flows by the lube relief valve and goes to the pump drive and speed increaser lube circuit. Excess lube oil is bypassed to sump through the lube relief valve.
Components of the transmission hydraulic system include a transmission hydraulic control, transmission gear pump, transmission hydraulic filter, transmission magnetic screen and a transmission oil cooler.
The transmission charging section of the transmission gear pump sends oil through the transmission hydraulic filter. The oil from the transmission charge pump section then goes to the transmission hydraulic control. The basic components of the transmission hydraulic control are the rotary actuator, and the selector and pressure control valve. This oil also supplies the lockup clutch solenoid, the upshift solenoid, and the downshift solenoid.
When the upshift solenoid or the downshift solenoid is activated, oil is sent to the rotary actuator. The rotary actuator turns the rotary selector spool in the selector and pressure control valve. This sends pilot oil in the pressure control valve to the clutch control stations which fill and modulate oil pressure to the clutches used in the new gear.