Hydraulic Components
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| Illustration 1 | g01727935 |
(1) Transmission output speed sensor (2) Pressure test ports (3) Torque converter inlet relief valve (4) Transmission hydraulic control relief valve (5) Lube relief valve (6) Converter inlet temperature sensor (7) Power train gear pump (8) Torque converter out pressure (9) Torque converter in pressure (10) Lockup clutch | |
Control of the transmission planetary is achieved by hydraulically actuated clutches that hold selected components of the planetary group stationary in order to allow the transmission of drive through the transmission.
Transmission Hydraulic System
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| Illustration 2 | g01308372 |
(8) Pressurized oil (9) ECPC solenoid (10) Modulating valve (11) Disengaged clutch (12) Engaged clutch | |
Oil is supplied by the transmission pump through a filter. The oil is available to each modulating valve (10) .
Control of the transmission planetary is achieved by hydraulically actuated clutches that hold selected components of the planetary group stationary. This allows the transmission of power in the selected gear (speed ratio) through the transmission.
Oil is supplied by the transmission pump through a filter. Oil (8) is available to each modulating valve (10) .
Shifting of the transmission is controlled by the electronic control module (ECM). The ECM acts in response to a variety of inputs.
Inputs to the ECM module include the following information.
- Selected Gear
- Engine Speed
- Transmission output speed
- High Gear Limit
The control of the transmission also accounts for factors such as the temperature of the transmission oil.
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 signals (PWM). The signals are sent by the ECM to individual solenoid (9) on each modulating valve (10) .
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 approximately proportional to the electrical current that is supplied to solenoid (9) that controls the clutch.
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| Illustration 3 | g00766511 |
A high current input is made initially. This overcomes the inertia of the valve and the clutch components and this initiates filling of the oil passage leading to the clutch piston. The current is reduced as the clutch is filled with oil and the plates move toward engagement. The current is held at a minimum value in order to allow the pressure of the oil in the clutch to increase slowly. The clearances between the plates and the disks are taken up smoothly. This period is called touchup. Once the plates and the disks are in contact, the current is increased gradually in order to ensure that maximum pressure is applied to the clutch in a smooth manner.
Electronic control of this process provides improved quality of transmission shifts.
A combination of clutches engages each of the seven forward gears.
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| Illustration 4 | g02625931 |
(4) Transmission hydraulic control relief valve (13) Oil filter (14) Modulating valve (Torque converter lockup clutch) (15) Torque converter input relief valve (16) Torque converter lockup clutch (17) Torque converter (18) Torque converter output relief valve (19) Transmission | |
Drive to the planetary transmission is through torque converter (17). The torque converter allows the speeds of the engine and the transmission to be matched smoothly. Once the speed of the engine and the transmission is matched, torque converter lockup clutch (16) engages in order to allow direct drive between the engine and the transmission.
Oil is supplied to the torque converter by Transmission hydraulic control relief valve (4) .
Oil from the torque converter flows through torque converter outlet relief valve (18) to the transmission. The torque converter outlet relief valve maintains a required pressure in the torque converter.
Transmission shifts are dictated by operating conditions. Transmission shifting is manual. Operator inputs can alter the shifting of the transmission. Examples of operator inputs are the selection of a highest permissible gear.