TUBE AS 2V7599 - Caterpillar

Transmission Hydraulic System
Illustration 1 g03516821
(1) Pressurized oil
(2) Solenoid (ECPC modulating valve)
(3) Modulating valve
(A) Test port (Clutch 1 pressure)
(B) Test port (Clutch 2 pressure)
(C) Test port (Clutch 3 pressure)
(D) Test port (Clutch 4 pressure)
(E) Test port (Clutch 5 pressure)
(F) Engaged clutch
(G) Disengaged clutch Oil is supplied by the transmission pump through a filter. Oil (1) is available to each modulating valve (3).Control of the transmission planetary is achieved by hydraulically actuated clutches. These clutches hold selected components of the planetary group stationary in order to allow the gear ratio drive 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
Output Speed
High Gear LimitThe 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 (2) on each modulating valve (3).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 solenoid (2) that controls the clutch.
Illustration 2 g00766511A high current input is made initially in order to overcome the inertia of the valve and the clutch components. The high current also 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. A gradual increase ensures 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 six forward gears and reverse gear.
Illustration 3 g03516824
(4) Oil filter
(5) Modulating valve pressure coupler
(6) Lockup clutch
(7) Torque converter lockup clutch
(8) Torque converter
(9) Oil to the transmission
(10) Transmission oil temperature sensor (converter outlet)
(11) Relief valve Power is supplied from the engine through the torque converter (8) and then to the planetary transmission. The torque converter (8) allows the speeds of the engine and the transmission to be matched smoothly. Once the speed of the engine and transmission is matched, torque converter lockup clutch (7) engages allowing direct drive between the engine and transmission.Oil is supplied to the torque converter by relief valve (11). Oil from the torque converter flows to the transmission cooler.Transmission shifts are dictated by operating conditions.