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| Illustration 1 | g03798274 |
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(1) Clutch 1
(2) Clutch 2 (3) Clutch 3 (4) Clutch 4 (5) Clutch 5 (6) Clutch 6 (7) Output shaft | |
| Speed Selection Clutch Engagement | |||||||
|---|---|---|---|---|---|---|---|
| Clutch 1 | Clutch 2 | Clutch 3 | Clutch 4 | Clutch 5 | Clutch 6 | LUC | |
| 1C | X | X | X | ||||
| 2L | X | X | X | X | |||
| 3L | X | X | X | X | |||
| 4L | X | X | X | X | |||
| 5L | X | X | X | X | |||
| 6L | X | X | X | X | |||
| 7L | X | X | X | X | |||
| 8L | X | X | X | X | |||
| 9L | X | X | X | X | |||
| 1RC | X | X | X | ||||
| 2RC | X | X | X | ||||
| N | X | X | |||||
The planetary transmission has nine forward speeds and two reverse speeds.
"REVERSE" and "NEUTRAL" use only torque converter drive. At lower ground speeds, "FIRST" gear "FORWARD" will also use torque converter drive mode.
As the ground speed increases in "2F" gear, Direct Drive Mode is activated. When the signal from the torque converter output speed Sensor and the signal from the engine speed sensor indicate the same rpm, the Transmission ECM ENGAGES the lockup clutch to provide Direct Drive Mode. This strategy provides "1F", "2F", and "4F" for Direct Drive Mode when the load on the power train is light. Direct Drive Mode is more fuel efficient at higher ground speeds, but Torque Converter Drive Mode increases torque, or rimpull, at lower speeds. Rotational power from the torque converter is transferred to the transmission input shaft.
The torque converter is always in Direct Drive Mode for speeds "2F" through "9F". Direct Drive Mode is maintained during transmission shifting while the clutches DISENGAGE and ENGAGE, which maintains torque at the wheels. If shifting becomes harsh, the problem may be easily corrected by performing a Clutch Fill Calibration procedure, using Cat ET.
The two Transmission Output Speed Sensors (not shown) determine the speed and direction of the Output Shaft (7). The signal from these sensors is considered by the Transmission ECM for shifting strategies.
The electronic main relief valve (EMRV) sets a maximum clutch pressure based on engine torque. When a speed is selected, the ECM sends a signal to the EMRV to limit maximum pressure. Each clutch is controlled by an Electronic Clutch Pressure Control (ECPC) valve which controls the pressure at the individual clutch.
When the software in the Transmission ECM determines that a shift from one gear to the next is needed (either manually or automatically), the ECM energizes the solenoids of the transmission modulating valves, which send high-pressure oil to the respective clutch pistons. This pressure moves the piston toward the clutch discs and plates, compressing the discs and plates together. When the plates and discs reach ENGAGEMENT pressure, the respective Transmission Planetary will begin to rotate, causing the transmission output shaft to transfer the rotational power and speed to the output transfer gears at the speed range of the selected gear.