ENGINE AR 1W0543 - Caterpillar

Illustration 1 g03476372Control 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 transmission of drive through the transmission.Oil is supplied by the transmission pump via a filter. The oil (1) is available to each modulating valve (8). The modulating valves control the engagement of particular clutches within the transmission.Note: Clutch 5 is a relatively large clutch. The oil supply line to the solenoid for clutch 5 has a 5 mm (0.20 inch) orifice. This orifice prevents system pressure from dropping while clutch 5 is being filled.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
Ground 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 or more clutches and the subsequent engagement of the next selected clutches.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 the individual solenoid (4) on each modulating valve (8).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 (4) that controls the clutch.
Illustration 2 g00766511A high current input is made initially. This high current input overcomes the inertia of the valve and the clutch components, initiating filling of the clutch. 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 to ensure that maximum pressure is smoothly applied to the clutch.Electronic control of this process provides improved quality of transmission shifts.A combination of clutches engages each of the six forward gears and one reverse gear.
Illustration 3 g03480380Drive to the planetary transmission is