FITTING G 0682553 - Caterpillar

Illustration 1 g02613017
735/740 machinesDiagram of the Transmission/Chassis ECMThe Transmission/Chassis ECM electronically controls the following functions.
Backup Alarm
Transmission Shift Points
Secondary Steering
Neutral Start Function
Parking Brake
Hoist System
Ejector System Not all of the components in the diagram are required during basic machine operation.Overview
The ECM controls different systems on the machine. The following information is an overview of the systems that are controlled by the ECM.The ECM controls the transmission shift points. The basic components and corresponding requirements for shifting of the transmission are listed below:Shift Lever Sensor - The ECM must know the current gear position. The sensor for the shift lever provides a PWM signal. The PWM signal varies with the gear that has been selected.Transmission Output Speed Sensors (TOS) - The ECM must know the output speed of the transmission. Two TOS tells the ECM the speed of the transmission output shaft. The TOS provides this information. When the operator selects a forward gear, the ECM automatically shifts the transmission. The shift is dictated by the transmission output speed. The automatic shift points are stored in the ECM. A shift occurs when the transmission output speed matches the shift point. When the TOS increases to a shift point the ECM activates the proper solenoids in order to change the transmission gear.Note: The transmission output speed is directly proportional to ground speed and engine speed. This activity occurs while the transmission is in direct drive. Shift points are based on the calculated engine speed. Two TOS sensors currently fitted for redundancyThe items that follow are exceptions.
When a shift from a forward gear or a shift from a reverse gear to "NEUTRAL" is made and the machine is moving faster than 8 km/h (5 mph), the ECM will not shift the transmission into neutral until the ground speed is less than 8 km/h (5 mph). This discourages coasting in neutral at high speed, which reduces transmission life. For more information, see the topic in System Operation, "Neutral Coast Function".
The reverse gear is not engaged until ground speed is less than 4.8 km/h (3 mph). This helps protect the transmission from damaging directional shifts. For additional information, see Systems Operation, "Reverse Shift Inhibit Function".
The ECM does not downshift when the operator selects a gear that is not appropriate for the current TOS. Automatic upshifting and/or downshifting will continue. The selected gear now becomes the new top gear.
The ECM shifts the transmission up one gear above the selected gear if the TOS reaches a critical value. This helps protect the engine from overspeed. If the transmission is already in top gear, the lockup clutch is deactivated. The ECM is designed to regulate the position of the hoist. The ECM energizes the solenoids that are used to control the raising and lowering of the body. This position is determined with information from both the operator and the machine.The ECM uses the status of the pressure for the primary steering and other inputs from the machine in order to control the secondary steering system.The ECM controls the parking