TRANSMISSION AR 2942711 - Caterpillar

Illustration 1 g00706658
Location of the Modulating Valves (Transmission Clutch) (1) Number 1 transmission modulating valve (Reverse) (2) Number 2 transmission modulating valve (Forward) (3) Number 3 transmission modulating valve (Fourth Speed) (4) Number 4 transmission modulating valve (Third Speed) (5) Number 5 transmission modulating valve (Second Speed) (6) Number 6 transmission modulating valve (First Speed) (7) Intermediate speed sensors (If Equipped)
Illustration 2 g00666134
Modulating Valve (Transmission Clutch)The transmission modulating valves are mounted on the top of the transmission under the cab. There is one modulating valve for each of the six transmission clutches.The modulating valves are outputs of the power train electronic control module (ECM). The transmission modulating valves are proportional solenoid valves. The modulating valves are used by the power train ECM to directly modulate the oil pressure that is sent to each individual clutch. When the operator selects a direction or when the operator selects a speed the power train ECM sends a pulse width modulated signal (PWM) in order to vary the current to the clutch solenoid. The distance that is travelled by the solenoid plunger (valve) is proportional to the electrical current of the solenoid. The position of the solenoid plunger (valve) controls the oil pressure of the selected clutch. The amount of current that is sent to the modulating valve regulates the amount of oil pressure that is supplied to the selected clutch. When the power train ECM sends the maximum current to the modulating valve, the oil pressure in the clutch is at the maximum. When no current is sent to the modulating valve, the oil pressure in the clutch is at the minimum.The power train ECM will activate the modulating valves that are selected by the operator. Modulating valves (1) and (2) supply oil to the direction clutches. Modulating valves (3), (4), (5) and (6) supply oil to the speed clutches. In order for the machine to move, one speed clutch solenoid and one direction clutch solenoid must be energized. When the transmission is in neutral, only one modulating valve (3) is energized. When the transmission is shifted to neutral, the direction clutch solenoid is de-energized and the present speed clutch solenoid is energized.The modulating valves have a connector with two contacts. One contact receives power from the corresponding connector contact of the power train ECM (J1-11, J1-17, J2-1, J2-2, J2-7 and J2-8). The other contact of all the modulating valves join together. The contacts return power to connector contact J1-7 and J2-3 of the power train ECM.Note: The solenoid coils are not designed to be operated at 24 DCV directly. The power train ECM sends a 24 volt PWM signal at a duty cycle which provides an average voltage of about 12 volts to the solenoid coils. Do not energize the solenoid coils with 24 DCV (+battery). The life of the solenoid coils will be drastically reduced if the solenoid coils are energized with 24 DCV (+battery). If the solenoid coils must be energized by a source that is different from the power