 | |
| Illustration 1 | g01309516 |
Basic diagram for the power train systems | |
 | |
| Illustration 2 | g01309523 |
Location of the power train components (1) Engine (2) Torque converter (3) Torque converter updrive gears (4) Upper drive shaft (5) Transmission (6) Output transfer gears (7) Center drive shaft (8) Oscillating hitch drive shaft (9) Rear drive shaft (10) Rear differential (11) Front differential (12) Front final drives (13) Wheels and tires (14) Front drive shaft (15) Rear final drives | |
The power train is made up of four basic systems:
- Power Train/Chassis Electronic Control Module (ECM)
- Torque Converter and Updrive Gears
- Transmission and Transfer Gears
- Differentials and Final Drives
The four basic systems have a hydraulic connection, an electrical connection, a magnetic connection, or a mechanical connection.
The operation of the power train begins at the Power Train/Chassis Electronic Control Module (ECM). The Power Train/Chassis ECM receives information of the selected speed of operation through the shift lever position sensor in the electrical system. The Power Train/Chassis ECM uses the information from several switches and sensors in the electrical system to control the power train hydraulic system. This is done by energizing the appropriate solenoids.
The torque converter has a lockup clutch for direct drive and a one-way clutch for torque converter drive mode. During the torque converter drive mode, the torque converter hydraulically drives the transmission. The torque converter is fastened directly to the flywheel of the engine.
The Power Train/Chassis ECM will engage the torque converter lockup clutch when direct drive is necessary. When the torque converter lockup clutch modulating valve is energized, the torque converter lockup clutch is hydraulically engaged. The rotating housing of the torque converter becomes mechanically connected to the output shaft of the torque converter through the torque converter lockup clutch. The output shaft of the torque converter drives the torque converter updrive gears. The upper drive shaft mechanically connects the torque converter updrive gears to the transmission. The transmission is fastened directly to the output transfer gears. When the torque converter lockup clutch is not engaged, the torque converter drives the transmission hydraulically.
The transmission hydraulic control modulating valves hydraulically engage the correct transmission clutches which cause the mechanical connection to the transmission output shaft. This mechanically connects to the transmission input shaft to the output shaft and to the differentials. The transmission will not drive the output shaft unless power is flowing through the torque converter. The power that is flowing through the torque converter can be hydraulic or mechanical.
Seven hydraulically engaged clutches in the transmission provide seven forward speeds and one reverse speed. REVERSE, NEUTRAL, FIRST, SECOND, THIRD OR FOURTH speeds are selected manually. FIFTH through to SEVENTH speed are selected automatically.
Power is sent through the REVERSE gear in torque converter drive mode only. FIRST speed has both a torque converter drive and a direct drive. The torque converter will be in torque converter drive for a short time during SECOND, THIRD, FIFTH, SIXTH and SEVENTH speeds. FOURTH speed will remain in direct drive. This provides smoother engagement of the transmission clutches. The transmission output shaft is fastened directly to the output transfer gears and then to the front and rear differentials and the bevel gears. The differentials and the bevel gears are fastened directly to the axle housings.
Power is supplied from the engine to the torque converter. Power flows from the torque converter to the updrive gears. The power then flows to the transmission. If the transmission is in gear, power flows from the transmission through the output transfer gears to the front and rear differentials. The front and rear axles mechanically connect the differentials to the final drives. The final drives are connected to the wheels. Power is then sent to the tires.
The Power Train ECM uses the following input signals to ensure steady engagement of the clutches: a transmission input speed sensor and two transmission output speed sensors. When the output shaft of the transmission is rotating, the transmission output speed sensors electrically signal the Power Train/Chassis ECM that the machine has moved.
The lower section of the output transfer gear case is the oil reservoir for the power train system.
The transmission gear pump is located at the rear of the torque converter updrive housing. This is a two-section gear pump. The front section is the torque converter scavenge pump section and the rear section is the transmission charging pump section.
The torque converter scavenge pump section will pull oil from the bottom of the torque converter updrive housing through a suction screen. The suction screen is located in the bottom of the torque converter updrive housing. The oil from the bottom of the torque converter updrive housing is transferred to the oil reservoir in the output transfer gear case.
The transmission charging pump section pulls oil from the output transfer gear case oil reservoir through a magnetic screen. The oil flows from the transmission charging pump section to the transmission oil filter. The flow of oil is split after flowing through the transmission oil filter. Some of the oil is sent to the torque converter lockup clutch modulating valve. This oil also flows to the torque converter updrive gears for lubrication. The remaining oil is sent to the transmission hydraulic control.
The oil that is sent to the torque converter lockup clutch modulating valve is used to engage the torque converter lockup clutch. When the lockup clutch modulating valve is energized by the Power Train/Chassis ECM, the lockup clutch modulating valve will send oil to the lockup clutch. The lockup clutch is engaged. The machine will be in direct drive. When the lockup clutch modulating valve is de-energized, the lockup clutch modulating valve will allow the oil in the lockup clutch to drain to the torque converter updrive housing. The lockup clutch will disengage and the machine will be in torque converter drive mode.
The relief valve in the transmission hydraulic control will control the maximum pressure in the transmission charging system. When the relief valve opens, oil is sent past the torque converter inlet relief valve and to the torque converter. If the torque converter inlet oil pressure becomes too high, the torque converter inlet relief valve will open. This oil will flow into the transmission case.
The oil that is sent to the torque converter is used as the hydraulic coupling inside the torque converter. The oil exits the torque converter through the torque converter outlet relief valve. The torque converter outlet relief valve will control the pressure of the oil inside the torque converter in order to keep the torque converter full of oil at all times.
The oil flows from the torque converter outlet relief valve to the power train oil cooler. The oil is sent from the power train oil cooler to the transmission for lubrication and cooling. This oil is then deposited in the transmission case where it flows back to the oil reservoir in the output transfer gear case.