Park - Engine Running

Park - Engine Running:

Description:

PARK - (Engine Running)

With the gear selector lever in the Park (P) position and the engine running, line pressure from the oil pump assembly is directed to various components in the valve body and oil pump.

PRESSURE REGULATION

Pressure Regulator Valve: Regulates oil pump output (line pressure) in response to torque signal fluid pressure, spring force and line pressure acting on the end of the valve. Line pressure is routed through the valve and into both the converter feed and decrease fluid circuits. Regulated line pressure is also directed to the manual valve, converter clutch signal valve and actuator feed limit valve.

Pressure Relief Valve: Controlled by spring force, this check-ball limits the maximum value of line pressure. When line pressure reaches this limiting value, fluid is exhausted past the ball and returns to the sump.

Line Pressure Tap: Provides a location to measure line pressure with a fluid pressure gage.

Actuator Feed Limit (AFL) Valve: Biased by spring force and orificed AFL fluid, it limits the maximum value of line pressure entering the AFL fluid circuit. Below this limiting value, AFL fluid pressure equals line pressure. AFL fluid is routed to the pressure control solenoid, 3-2 control solenoid, shift solenoids "A" and "B", and the 2-3 shift valve train.

Pressure Control Solenoid: Controlled by the Powertrain Control Module (PCM), it regulates filtered AFL fluid into torque signal fluid pressure. This regulation is controlled by varying the current value to the solenoid in relation to throttle position and other vehicle operating conditions.

TORQUE CONVERTER CLUTCH (TCC)

Torque Converter Clutch Signal Valve: The valve may be in a position to allow line pressure to enter the converter clutch (CC) signal fluid circuit. If this occurs with the 2nd clutch fluid circuit empty, Converter Clutch (CC) signal fluid pressure orificed to the end of the CC signal valve will close the valve and block line pressure. Any fluid in the CC signal fluid circuit will exhaust through the normally open and closed Torque Converter Clutch (TCC) solenoid.

Converter Clutch Apply Valve: Held in the release position by spring force, it directs converter feed fluid into the release fluid circuit. Also, fluid returning from the converter in the apply fluid circuit is routed through the valve and into the cooler fluid circuit.

Torque Converter: Release fluid pressure unseats the TCC apply checkball (#9), keeps the pressure plate released from the converter cover and fills the converter with fluid. Fluid exits the converter between the converter hub and stator shaft in the apply fluid circuit.

Cooler and Lubrication System: Cooler fluid from the converter clutch apply valve is routed through the transmission fluid cooler and into the lubrication fluid circuits.

Manual Valve: Controlled by the selector lever and manual shaft, the manual valve is in the Park (P) position and directs line pressure into the PR (Park/Reverse) fluid circuit. Line pressure is blocked from entering any other fluid circuit at the manual valve.

LO AND REVERSE CLUTCH APPLIES

Lo and Reverse Clutch Piston: PR fluid seats the lo/reverse clutch checkball (#10) and is orificed to the outer area of the piston. Orificing PR fluid around the #10 checkball helps control the lo and reverse clutch apply. Also, lo/reverse fluid pressure from the lo overrun valve acts on the inner area of the lo and reverse clutch piston to increase the clutch holding capacity.

Lo Overrun Valve: PR fluid pressure moves the valve against spring force and fills the lo/reverse fluid circuit. Lo/reverse fluid is orificed (#23) back to the lo/overrun valve to assist PR fluid in moving the valve against spring force. Spring force provides a time delay for PR fluid filling the lo/reverse fluid circuit. Lo/reverse fluid is routed to the inner area of the lo and reverse clutch piston to increase the holding capacity of the clutch.

Pressure Switch Assembly (PSA): The PSA consists of five fluid pressure switches: D2 and D3 are normally closed and D4, Lo and Rev are normally open. All fluid circuits routed to the assembly are empty and the PSA signals the PCM that the transmission is in either Park or Neutral.

Shift Solenoids ("A" and "B"): Both shift solenoids, which are normally open, are energized by the PCM and block fluid from exhausting. This maintains AFL fluid pressure at solenoid "B" and signal "A" fluid pressure at solenoid "A".

Shift Valves (1-2, 2-3 and 3-4): Signal "A" fluid pressure holds the 1-2 shift valve in the downshifted position and the 3-4 shift valve in the upshifted (First and Fourth gear) position. AFL fluid pressure from shift solenoid "B" holds the 2-3 shift valve train in the downshifted position.