When the gear selector lever is moved to the Reverse (R) position - from the Park position, the following changes occur in the transmission's hydraulic and electrical systems:

Pressure Regulation

Manual Valve: With the manual valve in the reverse position, line pressure is directed into the reverse fluid circuit.

Reverse Lockout Valve: Reverse fluid is routed through the reverse lockout valve into the reverse lockout fluid circuit.

Pressure Regulator and Line Boost Valves: Reverse clutch fluid at the line boost valve boosts line pressure for the additional torque requirements in Reverse. Throttle signal fluid pressure from the pressure control - PC solenoid acting on the line boost valve also helps determine line pressure in Reverse depending on throttle position and other TCM input signals.

Low and Reverse Clutch Applies

#8 Ball Check Valve and Orifice #12: Located in the bottom channel plate, reverse lockout fluid seats the #8 ball check valve against the low and reverse clutch fluid passage and directs fluid into the low and reverse clutch or reverse lockout fluid passage. Reverse lockout fluid pressure is also orificed, through orifice #12, to provide a controlled apply of the low and reverse clutch.

Low and Reverse Clutch: Low and reverse clutch or reverse lockout fluid pressure enters the outer area of the low and reverse clutch piston and moves the piston against spring force to apply the low and reverse clutch plates. In addition, reverse lockout fluid pressure is orificed into the inner area of the low and reverse clutch piston and provides additional force to apply the low and reverse clutch plates.

Reverse Clutch Applies

Note: Remember that the function of an orifice is to control the flow rate of fluid and rate of apply or release of a clutch.

#1 Ball Check Valve: Located in the bottom channel plate, reverse lockout fluid seats the #1 ball check valve and is forced through orifice #13 in the control valve body spacer plate into the reverse clutch fluid passage.

Reverse Clutch: Reverse clutch fluid enters the reverse clutch housing and acts on the reverse clutch piston to apply the reverse clutch plates.

Fluid Pressure Directed in Preparation for TCC Apply

#2 Ball Check Valve: Located in the bottom channel plate, reverse fluid seats the #2 ball check valve against the 2345 fluid passage and directs fluid into the 2345 or reverse fluid passage.

Torque Converter Clutch Pulse Width Modulation - TCC PWM Solenoid Valve: The TCC PWM solenoid valve remains de-energized - OFF. 2345 or reverse fluid is prevented from entering the TCC signal fluid circuit. Under normal circumstances the TCC PWM solenoid valve is not energized. In the event the TCC PWM solenoid valve is energized - when engaging Reverse while driving in Forward above a certain speed, TCC signal fluid will shift the reverse lockout valve to block reverse fluid from entering the reverse lockout circuit and the reverse clutch and the low and reverse clutch will release to prevent damage to the transmission.

Reverse