SHAFT AS 3T4006 - Caterpillar

Solenoids
The solenoid valves are some of the outputs of the Transmission ECU. These solenoids are the proportional type. The ECU uses a pulse width modulated signal (PWM) to vary the current to the solenoid. The distance that is travelled by the solenoid valve is proportional to the electrical current. The position of the valve controls the flow of the oil to the hydraulic cylinder.Transmission Shift Solenoids
Illustration 1 g01237747
The solenoid will work for either 12 Volt or 24 volt systems. The medium 12 volt ECPC valve will be used for all transmission clutches and the lockup clutch. This solenoid valve is driven by a pulse width modulated signal from the ECU.When a clutch solenoid is shorted to ground or an opened circuit, then all gears that use that clutch are not available. If a clutch solenoid is shorted to +battery, then only gears with that clutch are available. If more than one clutch is shorted to +battery, then the control cannot do anything and goes to no clutch neutral until fixed. Whenever a clutch solenoid has failed, the lockup clutch is turned off. The software will keep a list of available gears when a diagnostic trouble code occurs. If the control lever selects neutral, then the only way to get back to a selected gear is by shifting to neutral and then back into gear. For example, if the transmission is in reverse and clutch 3 is an opened circuit, then the transmission shifts to neutral and stays there until the operator selects neutral and reselects either forward or reverse. When a diagnostic trouble code occurs, if the current gear is available, then the control will remain in that gear. But if the diagnostic trouble code is present on an active clutch, then the software has to determine the appropriate desired gear. When a diagnostic trouble code goes active, the default logic will pick the next available lower gear as long as the output speed does not exceed the maximum output speed allowed for that gear. If a lower gear is not available or the output speed is too high for that gear, then select the next higher gear available. Transmission Lockup Clutch Solenoid
Illustration 2 g01237747
The Transmission ECU uses the solenoid valve to directly modulate the oil pressure to each transmission clutch. The ECU uses a pulse width modulated signal in order to vary the current to the solenoid. The solenoid current determines the amount of oil pressure that is applied to each clutch. The travel distance of the solenoid plunger is proportional to the amount of electrical current that is being sent to the solenoid. The position of the solenoid plunger controls the amount of oil pressure and the amount of clutch engagement. An increase in the electrical current will open the solenoid valve further. This causes and increase in oil pressure.The transmission lockup clutch solenoid connects to the ECU at contact J1-60 and contact J1-62.Output Drivers
Note: If you are experiencing problems with a driver that has been replaced, see