RAM 2500 Truck 2WD V8-5.7L (2008)
Fluid Pressure Sensor/Switch: Description and Operation
68RFE Automatic Transmission
Description
DESCRIPTION
The TCM utilizes a closed-loop system to control transmission line pressure. The system contains a variable force style solenoid, the Pressure Control
Solenoid, which is part of the pressure switch assembly. The solenoid is duty cycle controlled by the TCM to vent the unnecessary line pressure supplied
by the oil pump back to the pump inlet. The system contains a Line Pressure Sensor, which is a direct input to the TCM. The line pressure sensor
monitors the transmission line pressure and completes the feedback loop to the TCM. The TCM uses this information to adjust its control of the pressure
control solenoid to achieve the desired line pressure.
Operation
OPERATION
The TCM calculates the desired line pressure based upon inputs from the transmission and engine. The TCM calculates the torque input to the
transmission and uses that information as the primary input to the calculation. The line pressure is set to a predetermined value during shifts, to ensure
consistent shift quality. During all other operation, the desired line pressure value is adjusted based on torque level and other transmission requirements.
