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| Illustration 1 | g03204505 |
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Basic diagram for the power train systems | |
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| Illustration 2 | g06302083 |
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(1) ECPC solenoid
(2) Modulating valve (3) Engaged clutch (4) Pressurized oil (5) Disengaged clutch | |
Oil is supplied by the transmission pump through a filter. The oil is available to each modulating valve (2).
Control of the transmission planetary is achieved by hydraulically actuated clutches that hold selected components of the planetary group stationary. Holding selected components allows the transition of power in the selected gear (speed ratio) through the transmission.
Shifting of the transmission is controlled by the electronic control module (ECM). The ECM acts in response to various inputs.
Inputs to the ECM module include the following information:
- Selected gear
- Engine speed
- Torque converter output speed
- Transmission output speed
- Gear limits
- Transmission oil temperature
- Torque converter outlet oil pressure
Shifting of the transmission gears involves the release of one clutch and the subsequent engagement of the next clutch.
Each clutch is engaged by hydraulic oil pressure that is supplied by the modulating valves. The modulating valves are controlled by pulse width modulated (PWM) signals. The signals are sent by the ECM to the individual solenoids (1) on each modulating valve (16).
For details of the operation of the modulating valves, refer to Systems Operation, Testing and Adjusting, "Modulating Valves (Electronic Clutch Pressure Control)".
The pressure of the oil in the clutches is proportional to the electrical current that is supplied to the solenoid (1) that controls the clutch.
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| Illustration 3 | g00766511 |
To fill a clutch, a high current input is made initially to overcome the inertia of the valve and the clutch components, and then initiates filling of the oil passage leading to the clutch piston. The current is reduced as the clutch piston is filled with oil and the plates move toward engagement. The current is held at a minimum value in order to allow the oil pressure in the piston cavity to increase slowly and smoothly take up the clearances between the disks and plates. This period is called touchup. Once touchup is achieved, current is increased gradually to ensure that maximum pressure is applied to the clutch piston in a smooth manner.
Electronic control of this process provides improved quality of transmission shifts.
The six forward gears are engaged by a combination of clutches.
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| Illustration 4 | g06302156 |
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(A) Transmission
(6) Oil filter (7) Modulating valve (Torque converter lockup clutch) (8) Torque converter input relief valve (9) Torque converter (10) Transmission hydraulic control relief valve | |
Power is supplied from the engine, through torque converter (9), and then to the planetary transmission.
The torque converter (9) allows the speeds of the engine and the transmission to be matched smoothly and improve operating efficiency. Once the speed of the engine and transmission match, torque converter (9) engages in order to allow direct drive between the engine and transmission.
Oil is supplied to the torque converter by transmission hydraulic control relief valve (10).
Oil from the torque converter flows to the transmission oil cooler. Oil from the transmission oil cooler then flows to the planetary lube circuit.