Automatic Transmission - 4et50 - Description and Operation Cadillac ELR I

Driver Shift Control

Driver shift control (DSC) allows the driver to change gears similar to a manual transmission. Refer to the vehicle owner's manual for specific DSC operating instructions.

Scheme 1

Source Code for Plant

1. 4 - Ramos Arizpe, Mexico
2. H - N.mpsilanti, Michigan
3. J - Windsor, Ontario
4. S - Strasbourg, France
5. W - Warren, Michigan
6. Y - Toledo, Ohio
7. R - Boryeong, Korea
8. M - N.man Tai, Shan Dong, China
9. P - San Luis Potosi, Mexico
10. S - Silao, Mexico

Transmission General Description

The MKA 4ET50 is a fully automatic, front wheel drive transaxle, variable-speed, electronic-controlled transmission. It consists primarily of a torque dampener assembly, an integral main and auxiliary fluid pump and housing, 1 planetary gear set, 2 friction (rotating) and 1 mechanical (stationary) clutch assemblies, a hydraulic pressurization and control system, and two internal electric motors. Drive motor generator A (1) is 55 kW and drive motor generator B (2) is 111 kW.

The torque dampener contains internal torsional springs, fluid, input shaft and a clutch. The torque dampener acts as a spring coupling to smoothly transmit power from the engine flexplate to the transmission. The dampener provides a mechanical direct drive coupling of the engine to the transmission. The clutch is applied during engine starting and stopping events.

The planetary gear set provides the Electrically Variable forward mode ratios and reverse. Changing ratios is fully automatic and is accomplished through the use of a transmission control module (TCM) located inside the transmission and the drive motor generator power inverter module located under hood. Both the TCM and the drive motor generator power inverter module receives and monitors various electronic sensor inputs and uses this information to vary the torque output at the optimum time based on throttle position.

The TCM commands shift solenoids and variable bleed pressure control solenoids to control torque timing and feel. All the solenoids, including the TCM, are packaged into a self-contained control solenoid valve assembly.

The main hydraulic system primarily consists of a gerotor-type pump, control valve body assemblies, dampener housing and case. The pump maintains the working pressures needed to stroke the clutch pistons that apply or release the friction components. These friction components, when applied or released, support the automatic ratios qualities of the transmission.

The hydraulic system also uses a secondary system and consists of an auxiliary pump located inside of the transmission. This is a gerotor-type pump, electric three phase High Voltage motor, electric harness, and control module. The control module is located inside of the drive motor generator power inverter module under the hood. This pump maintains working pressures when the engine is off.

The friction components used in this transmission consist of 3 multiple disc clutches. The multiple disc clutches combine with a planetary gear set and electric motor to deliver the different ratios, forward and reverse. The gear set then transfers torque through the final drive assembly.

The transmission may be operated in any of the following gear ranges

Transmission Component and System Description

The mechanical components of the Electric Range Extended Vehicle MKA 4ET50 Transmission are as follows

1. Torque dampener assembly
2. Gerotor-type main fluid pump assembly
3. Gerotor type auxiliary fluid pump assembly
4. Input shaft
5. Drive motor generator assembly A (1) and B (2)
6. Internal gear assembly
7. Sun gear carrier assembly
8. VL 1-2R, C2-3-4, and C1-3R clutch housing assembly
9. Main shaft assembly
10. Center support assembly
11. Output shaft assembly
12. Control valve body assembly

The electrical components of the EREV MKA 4ET50 are as follows

1. Drive Motor Generator A (1) 55kW
2. Drive Motor Generator B (2) 111kW
3. Output speed sensor assembly
4. Manual shift shaft position switch
5. Control solenoid valve assembly, which contains the following components: Transmission control module (TCM) 6 variable bleed pressure control (PCS) solenoids 4 transmission fluid pressure (TFP) switch assemblies Torque dampener clutch pressure control solenoid (PCS5) 2 shift solenoids

For more information, refer to Electronic Component Description .

Transmission Adaptive Functions

The 4ET50 transmission utilizes a line pressure control system during clutch fill to compensate for the normal wear of transmission components. As the apply components within the transmission wear or change over time, shift time (the time required to apply a clutch) increase or decreases. In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various PC solenoids, to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as "adaptive learning" and it is used to ensure consistent shift feel plus increase transmission durability. The TCM monitors the A/T input speed and the A/T output speed sensor during commanded shifts to determine if a shift is occurring too fast, harsh, or too slow, soft, and adjusts the corresponding pressure control solenoid signal to maintain the set shift feel.

The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle.

Transmission Indicators and Messages

No transmission-related indicators or messages are displayed on the instrument panel cluster (IPC). For a complete listing and description of all vehicle indicators and messages, refer to Indicator/Warning Message Description and Operation.

Electronic Components

The 4ET50 transmission contains the electronic components listed below

1. A/Trans Manual Shift Shaft Position Switch Assembly
2. A/Trans Output Speed Sensor Assembly
3. Control solenoid valve assembly
4. Drive motor/generator assembly - unit A
5. Drive motor/generator assembly - unit B
6. Electric auxiliary fluid pump motor assembly

This transmission operates in 4 electronically variable transmission modes. High voltage three phase cables connect the 2 motor/generators and the electric auxiliary fluid pump drive motor assembly, to the drive motor control modules. The high voltage electric auxiliary fluid pump drive provides transmission fluid pressure during engine-off operation.

Scheme 2

Scheme 3

The drive motor generator power inverter module controls the three permanent magnet 3-phase electric motors that are internal to the transmission, and perform the following functions

1. Torque for vehicle propulsion
2. Engine cranking
3. Battery charging
4. Regenerative Braking
5. Transmission fluid pressure during engine-off operation

The Drive Motor/Generator Description

Drive motor/generator assembly - Unit A is a generator referred to as Motor 1 on the scan tool and consists of a permanent magnet rotor with a concentrated wound stator capable of producing 58 kW of peak electrical energy and 185 N.m (136 lb ft) of torque at 300V.

Drive motor/generator assembly - Unit B is a traction motor referred to as Motor 2 on the scan tool and consists of a permanent magnet rotor with a bar wound stator capable of producing 116 kW of peak electrical energy and 370 N.m (273 lb ft) of torque at 300V.

Both are actively cooled via transmission fluid. The drive motor/generator assembly - unit A is used to start the engine and maintain charge to the hybrid battery. The drive motor/generator assembly - unit B propels the vehicle. Motor speeds are controlled and monitored by resolver-type position sensors. The drive motor generator position sensors are monitored by the motor control modules. The motor control modules monitor the angular position, speed and direction of the drive motor generator based upon the signals of these position sensors. The position sensor, or resolver, contains a drive coil, 2 driven coils and an irregular shaped metallic rotor. The metallic rotor is mechanically attached to the shaft of the drive motor generator. At ignition ON, the motor control module outputs a 5 volt ac, 10 kHz excitation signal to the drive coil. The drive coil excitation signal creates a magnetic field surrounding the 2 driven coils and the irregular shaped rotor. The motor control module then monitors the 2 driven coil circuits for a return signal. The position of the irregular shaped metallic rotor causes the magnetically-induced return signals of the driven coils to vary in size and shape. A comparison of the 2 driven coils signals allows the motor control module to determine the exact angle, speed and direction of the drive motor generator. For more information on the drive motor function and system interaction refer to Drive Motor Generator Power Inverter Module Description and Operation .

Regenerative Braking On Demand

Regenerative Braking On Demand enables drivers to actively re-capture energy when slowing down, such as when approaching slower traffic or setting up for a tight turn. To engage Regenerative Braking On Demand, the driver releases the accelerator and pulls back on either the left or right steering-wheel paddle to begin regenerating electricity. When engaged, Regenerative Braking On Demand provides vehicle deceleration that is more than what a typical vehicle experiences while coasting, providing control and dynamic performance characteristics similar to downshifting in a manual-transmission vehicle. The feature does not bring the vehicle to a full stop. Releasing the paddle disengages Regenerative Braking On Demand, allowing the vehicle to coast normally. The driver can engage and disengage Regenerative Braking On Demand as desired and as traffic conditions allow.

Scheme 4

The electric auxiliary fluid pump motor assembly is driven by 300V alternating current which is controlled by the drive motor/generator power inverter module assembly. The purpose of the auxiliary fluid pump motor is to supply oil pressure to the transmission for lube, cooling and clutch application during vehicle propulsion when the engine is off and the main transmission pump is not operating. The auxiliary fluid pump motor is commanded on when propulsion is active and the internal combustion engine is Off.

Scheme 5

The control solenoid valve assembly contains the following components

1. Transmission control module
2. Clutch pressure control solenoids
3. Shift solenoids
4. Line pressure control solenoid
5. Transmission fluid temperature sensor
6. Transmission fluid pressure switches

These components are not serviced separately. The control assembly utilizes a lead-frame system to connect these components electrically to the transmission control module. No wires are used for these components. The control solenoid assembly bolts directly to the valve body assembly within the transmission. The control solenoid assembly X1 connector connects to the engine harness.

Scheme 6

The A/Trans manual shift shaft position switch assembly is a dual sliding hall-effect switch attached to the control valve body within the transmission. The 9 outputs from the switch indicate which position is selected by the transmission manual shaft. Four outputs (A, B, C, P), are range selection inputs to the transmission control module. The five (R1, R2, D1, D2, S) direction selection inputs to the hybrid/EV powertrain control module 1 through the transmission X175 24-way connector. The input voltage at the modules is high when the switch is open and low when the switch is closed. The state of each input is displayed on the scan tool as Internal Mode Switch Range and Internal Mode Switch 2. The Internal Mode Switch Range input parameters represented are transmission range signal A, signal B, signal C and signal P. The Internal Mode Switch 2 parameters represented are transmission direction signal R1, signal R2, signal D1, signal D2 and signal S.

Scheme 7

The output speed sensor assembly has 2 internal hall-effect type sensors, and is capable of sensing both speed and direction. The output speed sensor mounts to the A/Trans case assembly and is connected to the control solenoid assembly through a wire harness and connector. The sensor faces the front differential drive pinion (w/transfer gear) gear assembly machined teeth surface. The sensor receives 8.3-9.3 volts on the OSS supply voltage circuit from the transmission control module. As the output shaft rotates, the sensor produces a signal frequency based on the machined surface of the output shaft.

The 2 sensor elements in the output speed sensor assembly are spaced approximately 1/2 a tooth apart.

1. When the vehicle is moving in a forward direction, sensor A detects a particular tooth before sensor B.
2. When the vehicle is moving in a reverse direction, sensor B detects a particular tooth before sensor A.

The electronics in the sensor combine the 2 signals and send a signal with a different pulse width. This signal is interpreted by the transmission control module for speed and direction and is transmitted through the serial data circuits to the engine control module and the hybrid/EV powertrain control module 1. The engine control module, hybrid/EV powertrain control module 1, and transmission control module compare the output speed sensor signal with the anti-lock brake system wheel speed sensor signal. The hybrid/EV powertrain control module 1 also compares the output shaft direction with the drive motor 1 and drive motor 2 direction.

Park Engine Off

When the gear selector lever is in the Park (P) position and the internal combustion engine is OFF, the auxiliary fluid pump is commanded ON and line pressure is directed to the pressure regulator valve.

Fluid Pressure Directed in Preparation for a Shift

Variable Low and 1-2 Reverse Clutch Regulator Valve

Line or auxiliary line fluid is routed through orifice #25 to the variable low and 1-2 reverse clutch regulator valve in preparation for a shift.

Variable Hi and 2-3-4 Clutch Regulator Valve

Line or auxiliary line fluid is routed through orifice #23 to the variable hi and 2-3-4 clutch regulator valve in preparation for a shift.

1-3 Reverse Clutch Regulator Valve

Line or auxiliary line fluid is routed through orifice #24 to the 1-3 reverse clutch regulator valve in preparation for a shift.

Dampener Bypass Clutch Valve

Line or auxiliary line fluid is routed through orifice #29 to the dampener bypass clutch valve in preparation for an apply of the torque dampener clutch.

Dampener Clutch Charge

Line or auxiliary line fluid is routed through orifices #42 and #43 into the dampener clutch charge circuit. Dampener clutch charge fluid fills the torque dampener clutch assembly in preparation for an apply of the torque dampener clutch.

Scheme 8

Park Engine On

When the transmission is operating in Park (Engine OFF), and the HPCM determines that vehicle operating conditions (low state of battery charge) are appropriate, the internal combustion engine (ICE) is started, the auxiliary fluid pump is turned OFF, and the main fluid pump provides hydraulic fluid pressure (refer to Engine Start ). After Engine Start, the following changes would occur to the transmission's hydraulic and electrical systems.

1-3 Reverse Clutch Releases

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is commanded OFF, allowing PCS 4 signal fluid to exhaust from the 1-3 reverse clutch regulator valve.

Shift Solenoid 2

The shift solenoid 2 is commanded OFF, allowing solenoid 2 signal fluid to exhaust. When solenoid 2 signal fluid exhausts, the shift solenoid valve- mode A moves to the released position.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid pressure is exhausted from the 1-3 reverse clutch housing assembly, allowing 1-3 reverse clutch spring force to move the 1-3 reverse clutch piston and release the 1-3 reverse clutch plates.

Shift Solenoid Valve- Mode A

13 reverse clutch fluid pressure exhausts at the shift solenoid valve- mode A.

#3 Ball Check Valve

13 reverse clutch feedback fluid pressure exhausts into the 13 reverse clutch/A cooling feed circuit, allowing actuator feed limit fluid to seat the ball.

1-3 Reverse Clutch Regulator Valve

1-3 reverse clutch regulator valve spring force moves the 1-3 reverse clutch regulator valve to the released position, allowing 13 reverse clutch/A cooling feed fluid pressure to exhaust.

Torque Dampener Clutch Releases

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is de-energized (OFF) allowing PCS 5 signal fluid to exhaust from the dampener bypass clutch valve.

Torque Dampener Clutch Assembly

Dampener clutch fluid exhausts from the torque dampener clutch assembly to the dampener bypass clutch valve allowing the torque dampener clutch to release.

Dampener Bypass Clutch Valve

Dampener bypass clutch valve spring force moves the dampener bypass clutch valve to the released position, allowing dampener clutch fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

Dampener clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

Shift Accumulation

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid also exhausts from the 1-3 reverse clutch accumulator assembly. Accumulator spring force moves the 1-3 reverse clutch accumulator piston to the released position.

Scheme 9

Neutral Engine Off

When the gear selector lever is moved to the Neutral (N) position, the hydraulic and electrical system operation is identical to Park (P) range. However, if Neutral is selected after the vehicle was operating in Reverse (R), the following changes would occur in the hydraulic system.

If the transmission is operating in Reverse, and the internal combustion engine is ON when a shift to Neutral occurs, the 1-3 reverse clutch is released.

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is commanded OFF, allowing PCS 4 signal fluid to exhaust from the 1-3 reverse clutch regulator valve.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid pressure is exhausted from the 1-3 reverse clutch housing assembly, allowing 1-3 reverse clutch spring force to move the 1-3 reverse clutch piston and release the 1-3 reverse clutch plates.

Shift Solenoid Valve - Mode A

13 reverse clutch fluid pressure exhausts at the shift solenoid valve- mode A.

#3 Ball Check Valve

13 reverse clutch feedback fluid pressure exhausts into the 13 reverse clutch/A cooling feed circuit, allowing actuator feed limit fluid to seat the ball.

1-3 Reverse Clutch Regulator Valve

1-3 reverse clutch regulator valve spring force moves the 1-3 reverse clutch regulator valve to the released position, allowing 13 reverse clutch/A cooling feed fluid pressure to exhaust.

Variable Low and 1-2 Reverse Clutch Releases

If the transmission is operating in Reverse- Series Mode when a shift to Neutral occurs, the variable low and 1-2 reverse clutch is released.

Pressure Control (PC) Solenoid 3

The PC solenoid 3 is de-energized (OFF) allowing PCS 3 signal fluid to exhaust from the variable low and 1-2 reverse clutch regulator valve; the variable low and 1-2 reverse clutch boost valve; and the shift solenoid valve-mode B.

Variable Low and 1-2 Reverse Clutch Assembly

VL 12 reverse clutch fluid exhausts from the variable low and 1-2 reverse clutch to the shift solenoid valve- mode B allowing the variable low and 1-2 reverse clutch to release.

Shift Solenoid Valve- Mode B

VL 12 reverse clutch fluid passes through the shift solenoid valve- mode B and into the VL 12 reverse clutch feed fluid circuit and is routed to the variable low and 1-2 reverse clutch regulator valve.

Variable Low and 1-2 Reverse Clutch Boost Valve

Variable low and 1-2 reverse clutch boost valve spring force moves the variable low and 1-2 reverse clutch boost valve to the released position, allowing VL 12 reverse clutch feedback fluid pressure to exhaust into the VL 12 reverse clutch feed circuit.

Variable Low and 1-2 Reverse Clutch Regulator Valve

Variable low and 1-2 reverse clutch regulator valve spring force moves the variable low and 1-2 reverse clutch regulator valve to the released position, allowing VL 12 reverse clutch feed fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

VL 12 reverse clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

Variable Hi and 2-3-4 Clutch Releases

If the transmission is operating in Reverse- Output Split when a shift to Neutral occurs, the variable hi and 2-3-4 clutch is released.

Pressure Control (PC) Solenoid 2

The PC solenoid 2 is commanded OFF, allowing PCS 2 signal fluid to exhaust from the variable hi and 2-3-4 clutch regulator valve and the variable hi and 2-3-4 clutch boost valve.

Variable Hi and 2-3-4 Clutch Assembly

VH 234 clutch fluid pressure is exhausted from the case assembly, allowing variable hi and 2-3-4 clutch spring force to move the variable hi and 2-3-4 clutch piston and release the variable hi and 2-3-4 clutch plates.

Shift Solenoid Valve- Mode B

Exhausting VH 234 clutch fluid pressure passes through the shift solenoid valve- mode B into the VH 234 clutch feed circuit.

Shift Solenoid Valve- Mode A

VH 234 clutch feed fluid pressure exhausts at the shift solenoid valve- mode A.

Variable Hi and 2-3-4 Clutch Regulator Valve

Variable hi and 2-3-4 clutch regulator valve spring force moves the variable hi and 2-3-4 clutch regulator valve to the released position, allowing VH 234 clutch/B cooling feed fluid pressure to exhaust.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid also exhausts from the 1-3 reverse clutch accumulator assembly. Accumulator spring force moves the 1-3 reverse clutch accumulator piston to the released position.

Variable Low and 1-2 Reverse Clutch Accumulator

VL 12 reverse clutch fluid also exhausts from the variable low and 1-2 reverse clutch accumulator assembly. Accumulator spring force moves the variable low and 1-2 reverse clutch accumulator piston to the released position.

Variable Hi and 2-3-4 Clutch Accumulator

VH 234 clutch fluid also exhausts from the variable hi and 2-3-4 clutch accumulator assembly. Accumulator spring force moves the variable hi and 2-3-4 clutch accumulator piston to the released position.

Scheme 10

Neutral Engine On

When the transmission is operating in Neutral (Engine OFF), and the HPCM determines that vehicle operating conditions (low state of battery charge) are appropriate, the internal combustion engine (ICE) is started, the auxiliary fluid pump is turned OFF, and the main fluid pump provides hydraulic fluid pressure (refer to Engine Start ). After Engine Start, the following changes would occur to the transmission's hydraulic and electrical systems.

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is commanded OFF, allowing PCS 4 signal fluid to exhaust from the 1-3 reverse clutch regulator valve.

Shift Solenoid 2

The shift solenoid 2 is commanded OFF, allowing solenoid 2 signal fluid to exhaust. When solenoid 2 signal fluid exhausts, the shift solenoid valve- mode A moves to the released position.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid pressure is exhausted from the 1-3 reverse clutch housing assembly, allowing 1-3 reverse clutch spring force to move the 1-3 reverse clutch piston and release the 1-3 reverse clutch plates.

Shift Solenoid Valve - Mode A

13 reverse clutch fluid pressure exhausts at the shift solenoid valve- mode A.

#3 Ball Check Valve

13 reverse clutch feedback fluid pressure exhausts into the 13 reverse clutch/A cooling feed circuit, allowing actuator feed limit fluid to seat the ball.

1-3 Reverse Clutch Regulator Valve

1-3 reverse clutch regulator valve spring force moves the 1-3 reverse clutch regulator valve to the released position, allowing 13 reverse clutch/A cooling feed fluid pressure to exhaust.

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is de-energized (OFF) allowing PCS 5 signal fluid to exhaust from the dampener bypass clutch valve.

Torque Dampener Clutch Assembly

Dampener clutch fluid exhausts from the torque dampener clutch assembly to the dampener bypass clutch valve allowing the torque dampener clutch to release.

Dampener Bypass Clutch Valve

Dampener bypass clutch valve spring force moves the dampener bypass clutch valve to the released position, allowing dampener clutch fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

Dampener clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid also exhausts from the 1-3 reverse clutch accumulator assembly. Accumulator spring force moves the 1-3 reverse clutch accumulator piston to the released position.

Scheme 11

Engine Start

When the vehicle is operating with the internal combustion engine OFF and auxiliary fluid pump ON, and the HPCM determines that vehicle operating conditions (low state of battery charge) are appropriate for starting the internal combustion engine (ICE), it commands the following changes to the transmission's hydraulic and electrical systems.

Note. The illustration shown depicts an Engine Start event that occurs during vehicle operation in Park. However, Engine Start can occur in any transmission operating range.

Torque Dampener Clutch Applies

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is energized (ON) allowing actuator feed limit fluid to enter the PCS 5 signal circuit. PCS 5 signal fluid is then routed through orifice #13 to the dampener bypass clutch valve.

Dampener Bypass Clutch Valve

PCS 5 signal fluid, at the dampener bypass clutch valve, opposes dampener bypass clutch valve spring force and orificed dampener clutch fluid pressure to regulate line or auxiliary line pressure into the dampener clutch circuit. Dampener clutch fluid is routed to the torque dampener clutch.

Torque Dampener Clutch Assembly

A feed hole in the input shaft allows fluid to enter the torque dampener assembly behind the torque dampener clutch piston. Dampener clutch fluid pressure moves the dampener clutch piston against spring force to apply the dampener clutch plates. When fully applied, the dampener clutch apply plate, the dampener clutch plates, and the dampener clutch plate assemblies are locked together, forming a direct mechanical connection between the engine flywheel and the transmission input shaft. With the engine flywheel and transmission input shaft locked together, the HPCM is able to use the generator/drive motor- unit A to start the ICE. The torque dampener clutch may be applied in any range when the vehicle is operating with the internal combustion engine OFF.

1-3 Reverse Clutch Applies

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is energized (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #18 to the 1-3 reverse clutch regulator valve.

1-3 Reverse Clutch Regulator Valve

PCS 4 signal fluid, at the 1-3 reverse clutch regulator valve, opposes 1-3 reverse clutch regulator valve spring force and 13 reverse clutch feedback fluid pressure to regulate line or auxiliary line pressure into the 13 reverse clutch/A cooling feed circuit.

#3 Ball Check Valve

13 reverse clutch feedback fluid unseats the #3 ball check valve, allowing excess pressure to pass into the actuator feed limit circuit. This helps to control clutch apply fluid pressure and clutch apply feel.

Shift Solenoid Valve- Mode A

13 reverse clutch/A cooling feed fluid passes through the shift solenoid valve- mode A and enters the 13 reverse clutch circuit.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid passes through the case and the transmission fluid pump cover into the 1-3 reverse clutch housing and moves the 1-3 reverse clutch piston against spring force to apply the 1-3 reverse clutch plates.

#1 Pressure Switch

Solenoid 2 signal fluid passes through the 1-3 reverse clutch regulator valve into the PS1 fluid passage. PS1 fluid opens the normally closed #1 pressure switch, signaling the TCM that the transmission is in Engine Start.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid is also sent to the 1-3 reverse clutch accumulator assembly. 13 reverse clutch fluid moves the 1-3 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the 1-3 reverse clutch assembly.

Scheme 12

Reverse Output Split Engine Off

When the gear selector lever is moved to the Reverse (R) position (from the Park position), and the internal combustion engine (ICE) is OFF, the following changes occur in the transmission's hydraulic and electrical systems.

Variable Hi and 2-3-4 Clutch Applies

Pressure Control (PC) Solenoid 2

The PC solenoid 2 is energized (ON) allowing actuator feed limit fluid to enter the PCS 2 signal circuit. PCS 2 signal fluid is then routed through orifice #20 to the variable hi and 2-3-4 clutch regulator valve.

Shift Solenoid 1

The shift solenoid 1 is energized (ON) allowing actuator feed limit fluid to enter the solenoid 1 signal fluid circuit. Solenoid 1 signal fluid is then routed through orifice #32 to the shift solenoid valve - mode B.

Variable Hi and 2-3-4 Clutch Regulator Valve

PCS 2 signal fluid, at the variable hi and 2-3-4 clutch regulator valve, opposes variable hi and 2-3-4 clutch regulator valve spring force and VH 234 clutch feedback fluid pressure to regulate line or auxiliary line pressure into the VH 234 clutch/B cooling feed circuit.

Variable Hi and 2-3-4 Clutch Boost Valve

PCS 2 signal fluid pressure acts on a differential area of the variable hi and 2-3-4 clutch boost valve, moving the valve against variable hi and 2-3-4 clutch boost valve spring force to regulate VH 234 clutch/B cooling feed fluid into the VH 234 clutch feedback circuit. As PCS 2 signal fluid pressure is increased to a given value, the variable hi and 2-3-4 clutch boost valve opens the VH 234 clutch feedback circuit to exhaust. This results in the variable hi and 2-3-4 clutch regulator valve moving to the full feed position, sending full VH 234 clutch feed pressure (full line pressure) to the variable hi and 2-3-4 clutch.

Shift Solenoid Valve - Mode A

VH 234 clutch/B cooling feed fluid passes through the shift solenoid valve - mode A into the B cooling supply circuit and is routed to the shift solenoid valve - mode B.

Shift Solenoid Valve - Mode B

Solenoid 1 signal fluid moves the shift solenoid valve - B, against spring force, to the applied position. VH 234 clutch/B cooling feed fluid passes through the valve into the VH 234 clutch circuit and is routed to the variable hi and 2-3-4 clutch assembly.

Variable Hi and 2-3-4 Clutch Assembly

VH 234 clutch fluid is directed to the variable hi and 2-3-4 clutch piston to apply the variable hi and 2-3-4 clutch plates and achieve Reverse - Output Split.

Variable Hi and 2-3-4 Clutch Accumulator

VH 234 clutch fluid is also sent to the variable hi and 2-3-4 clutch accumulator assembly. VH 234 clutch fluid moves the variable hi and 2-3-4 clutch accumulator piston against accumulator spring force to cushion the apply of the variable hi and 2-3-4 clutch assembly.

Scheme 13

Reverse Output Split Engine On

When the transmission is operating in Reverse - Output Split (R), and the HPCM determines that operating conditions are appropriate, the internal combustion engine (ICE) is started, the auxiliary fluid pump is turned OFF, and the main fluid pump provides hydraulic fluid pressure (refer to Engine Start ). After Engine Start, the following changes would occur to the transmission's hydraulic and electrical systems.

1-3 Reverse Clutch Remains Applied

The 1-3 reverse clutch is applied for Engine Start, and remains applied for Reverse - Output Split (Engine ON).

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is energized (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #18 to the 1-3 reverse clutch regulator valve.

Shift Solenoid 2

The shift solenoid 2 is energized (ON) allowing actuator feed limit fluid to enter the solenoid 2 signal fluid circuit. Solenoid 2 signal fluid is routed through orifice #21 to the shift solenoid valve - mode A. Solenoid 2 signal fluid is also routed to the variable hi and 2-3-4 clutch regulator valve, and to the 1-3 reverse clutch regulator valve where it enters the PS1 fluid circuit.

1-3 Reverse Clutch Regulator Valve

PCS 4 signal fluid, at the 1-3 reverse clutch regulator valve, opposes 1-3 reverse clutch regulator valve spring force and 13 reverse clutch feedback fluid pressure to regulate line or auxiliary line pressure into the 13 reverse clutch/A cooling feed circuit.

#3 Ball Check Valve

13 reverse clutch feedback fluid unseats the #3 ball check valve, allowing excess pressure to pass into the actuator feed limit circuit. This helps to control clutch apply fluid pressure and clutch apply feel.

Shift Solenoid Valve - Mode A

Solenoid 2 signal fluid moves the shift solenoid valve - A, against spring force, to the applied position. 13 reverse clutch/A cooling feed fluid passes through the shift solenoid valve - mode A and enters the 13 reverse clutch circuit.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid passes through the case and the transmission fluid pump cover into the 1-3 reverse clutch housing and moves the 1-3 reverse clutch piston against spring force to apply the 1-3 reverse clutch plates.

#1 Pressure Switch

Solenoid 2 signal fluid passes through the 1-3 reverse clutch regulator valve into the PS1 fluid passage. PS1 fluid opens the normally closed #1 pressure switch, signaling the TCM that the transmission is in Reverse - Output Split.

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is de-energized (OFF) allowing PCS 5 signal fluid to exhaust from the dampener bypass clutch valve.

Torque Dampener Clutch Assembly

Dampener clutch fluid exhausts from the torque dampener clutch assembly to the dampener bypass clutch valve allowing the torque dampener clutch to release.

Dampener Bypass Clutch Valve

Dampener bypass clutch valve spring force moves the dampener bypass clutch valve to the released position, allowing dampener clutch fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

Dampener clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

Variable Hi and 2-3-4 Clutch Remains Applied

Variable Hi and 2-3-4 Clutch Assembly

When the transmission is operating in Reverse - Output Split, and the engine is ON, the variable hi and 2-3-4 clutch remains applied. The routing of apply fluid to the variable hi and 2-3-4 clutch is similar to that described for Reverse - Output Split (Engine OFF), with the exception that VH 234 clutch/B cooling feed fluid passes through the applied shift solenoid valve - mode A into the VH 234 clutch feed circuit.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid is also sent to the 1-3 reverse clutch accumulator assembly. 13 reverse clutch fluid moves the 1-3 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the 1-3 reverse clutch assembly.

Variable Hi and 2-3-4 Clutch Accumulator

VH 234 clutch fluid is also sent to the variable hi and 2-3-4 clutch accumulator assembly. VH 234 clutch fluid moves the variable hi and 2-3-4 clutch accumulator piston against accumulator spring force to cushion the apply of the variable hi and 2-3-4 clutch assembly.

Scheme 14

Reverse Series Mode Engine Off

When the transmission is operating in Reverse - Output Split (R) and the internal combustion engine is OFF, and the HPCM determines that operating conditions are appropriate, Reverse - Series Mode is commanded and the following changes occur in the transmission's hydraulic and electrical systems.

Variable Low and 1-2 Reverse Clutch Applies

Pressure Control (PC) Solenoid 3

The PC solenoid 3 is energized (ON) allowing actuator feed limit fluid to enter the PCS 3 signal circuit. PCS 3 signal fluid is then routed through orifice #30 to the variable low and 1-2 reverse clutch regulator valve; through orifice #12 to the variable low and 1-2 reverse clutch boost valve; and to the shift solenoid valve - mode B.

Shift Solenoid 1

The shift solenoid 1 is commanded OFF, allowing solenoid 1 signal fluid to exhaust. When solenoid 1 signal fluid exhausts, the shift solenoid valve - mode B moves to the released position.

Variable Low and 1-2 Reverse Clutch Regulator Valve

PCS 3 signal fluid, at the variable low and 1-2 reverse clutch regulator valve, opposes variable low and 1-2 reverse clutch regulator valve spring force and VL 12 reverse clutch feedback fluid pressure to regulate line or auxiliary line pressure into the VL 12 reverse clutch feed circuit.

Variable Low and 1-2 Reverse Clutch Boost Valve

PCS 3 signal fluid pressure acts on a differential area of the variable low and 1-2 reverse clutch boost valve, moving the valve against variable low and 1-2 reverse clutch boost valve spring force to regulate VL 12 reverse clutch feed fluid into the VL 12 reverse clutch feedback circuit. As PCS 3 signal fluid pressure is increased to a given value, the variable low and 1-2 reverse clutch boost valve opens the VL 1-2 reverse clutch feedback circuit to exhaust. This results in the variable low and 1-2 reverse clutch regulator valve moving to the full feed position, sending full VL 12 reverse clutch feed pressure (full line pressure) to the variable low and 1-2 reverse clutch.

Shift Solenoid Valve - Mode B

VL 12 reverse clutch feed fluid is routed to the shift solenoid valve - mode B, where it passes through the valve into the VL 12 reverse clutch circuit.

Variable Low and 1-2 Reverse Clutch Assembly

VL 12 reverse clutch fluid pressure enters the case assembly behind the variable low and 1-2 reverse clutch piston and moves the piston against spring force to apply the variable low and 1-2 reverse clutch plates.

Pressure Control (PC) Solenoid 2

The PC solenoid 2 is commanded OFF, allowing PCS 2 signal fluid to exhaust from the variable hi and 2-3-4 clutch regulator valve and the variable hi and 2-3-4 clutch boost valve.

Variable Hi and 2-3-4 Clutch Assembly

VH 234 clutch fluid pressure is exhausted from the case assembly, allowing variable hi and 2-3-4 clutch spring force to move the variable hi and 2-3-4 clutch piston and release the variable hi and 2-3-4 clutch plates.

Shift Solenoid Valve - Mode B

Exhausting VH 234 clutch fluid pressure passes through the shift solenoid valve - mode B into the 234 clutch feed circuit.

Shift Solenoid Valve - Mode A

Exhausting 234 clutch feed fluid pressure passes through the shift solenoid valve - mode A into the VH 234 clutch/B cooling feed circuit.

Variable Hi and 2-3-4 Clutch Regulator Valve

Variable hi and 2-3-4 clutch regulator valve spring force moves the variable hi and 2-3-4 clutch regulator valve to the released position, allowing VH 234 clutch/B cooling feed fluid pressure to exhaust.

Variable Low and 1-2 Reverse Clutch Accumulator

VL 12 reverse clutch fluid is also sent to the variable low and 1-2 reverse clutch accumulator assembly. VL 12 reverse clutch fluid moves the variable low and 1-2 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the variable low and 1-2 reverse clutch assembly.

Variable Hi and 2-3-4 Clutch Accumulator

VH 234 clutch fluid also exhausts from the variable hi and 2-3-4 clutch accumulator assembly. Accumulator spring force moves the variable hi and 2-3-4 clutch accumulator piston to the released position.

Scheme 15

Reverse Series Mode Engine On

When the transmission is operating in Reverse- Series Mode (R), and the HPCM determines that operating conditions are appropriate, the internal combustion engine (ICE) is started, the auxiliary fluid pump is turned OFF, and the main fluid pump provides hydraulic fluid pressure (refer to Engine Start ). After Engine Start, the following changes would occur to the transmission's hydraulic and electrical systems.

The 1-3 reverse clutch is applied for Engine Start, and remains applied for Reverse- Series Mode (Engine ON).

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is energized (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #18 to the 1-3 reverse clutch regulator valve.

Shift Solenoid 2

The shift solenoid 2 is energized (ON) allowing actuator feed limit fluid to enter the solenoid 2 signal fluid circuit. Solenoid 2 signal fluid is routed through orifice #21 to the shift solenoid valve- mode A. Solenoid 2 signal fluid is also routed to the variable hi and 2-3-4 clutch regulator valve, and to the 1-3 reverse clutch regulator valve.

1-3 Reverse Clutch Regulator Valve

PCS 4 signal fluid, at the 1-3 reverse clutch regulator valve, opposes 1-3 reverse clutch regulator valve spring force and 13 reverse clutch feedback fluid pressure to regulate line or auxiliary line pressure into the 13 reverse clutch/A cooling feed circuit.

#3 Ball Check Valve

13 reverse clutch feedback fluid unseats the #3 ball check valve, allowing excess pressure to pass into the actuator feed limit circuit. This helps to control clutch apply fluid pressure and clutch apply feel.

Shift Solenoid Valve - Mode A

13 reverse clutch/A cooling feed fluid passes through the shift solenoid valve- mode A and enters the 13 reverse clutch circuit.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid passes through the case and the transmission fluid pump cover into the 1-3 reverse clutch housing and moves the 1-3 reverse clutch piston against spring force to apply the 1-3 reverse clutch plates.

#1 Pressure Switch

Solenoid 2 signal fluid passes through the 1-3 reverse clutch regulator valve into the PS1 fluid passage. PS1 fluid opens the normally closed #1 pressure switch, signaling the TCM that the transmission is in Reverse- Series Mode.

#3 Pressure Switch

Solenoid 2 signal fluid passes through the variable hi and 2-3-4 clutch regulator valve into the PS3 fluid passage. PS3 fluid opens the normally closed #3 pressure switch, signaling the TCM that the transmission is in Reverse- Series Mode.

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is de-energized (OFF) allowing PCS 5 signal fluid to exhaust from the dampener bypass clutch valve.

Torque Dampener Clutch Assembly

Dampener clutch fluid exhausts from the torque dampener clutch assembly to the dampener bypass clutch valve allowing the torque dampener clutch to release.

Dampener Bypass Clutch Valve

Dampener bypass clutch valve spring force moves the dampener bypass clutch valve to the released position, allowing dampener clutch fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

Dampener clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

Variable Low and 1-2 Reverse Clutch Remains Applied

Variable Low and 1-2 Reverse Clutch Assembly

With the exception of the switch to line fluid pressure from the main fluid pump assembly, no other changes occur to the variable low and 1-2 reverse clutch fluid circuit and the variable low and 1-2 reverse clutch remains applied.

Pressure Control (PC) Solenoid 2

The PC solenoid 2 is commanded OFF, allowing PCS 2 signal fluid to exhaust from the variable hi and 2-3-4 clutch regulator valve and the variable hi and 2-3-4 clutch boost valve.

Variable Hi and 2-3-4 Clutch Assembly

VH 234 clutch fluid pressure is exhausted from the case assembly, allowing variable hi and 2-3-4 clutch spring force to move the variable hi and 2-3-4 clutch piston and release the variable hi and 2-3-4 clutch plates.

Shift Solenoid Valve- Mode B

Exhausting VH 234 clutch fluid pressure passes through the shift solenoid valve- mode B into the 234 clutch feed circuit.

Shift Solenoid Valve- Mode A

Exhausting 234 clutch feed fluid pressure passes through the shift solenoid valve- mode A into the VH 234 clutch/B cooling feed circuit.

Variable Hi and 2-3-4 Clutch Regulator Valve

Variable hi and 2-3-4 clutch regulator valve spring force moves the variable hi and 2-3-4 clutch regulator valve to the released position, allowing VH 234 clutch/B cooling feed fluid pressure to exhaust.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid is also sent to the 1-3 reverse clutch accumulator assembly. 13 reverse clutch fluid moves the 1-3 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the 1-3 reverse clutch assembly.

Variable Low and 1-2 Reverse Clutch Accumulator

VL 12 reverse clutch fluid is also sent to the variable low and 1-2 reverse clutch accumulator assembly. VL 12 reverse clutch fluid moves the variable low and 1-2 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the variable low and 1-2 reverse clutch assembly.

Variable Hi and 2-3-4 Clutch Accumulator

VH 234 clutch fluid also exhausts from the variable hi and 2-3-4 clutch accumulator assembly. Accumulator spring force moves the variable hi and 2-3-4 clutch accumulator piston to the released position.

Scheme 16

Drive Series Mode Engine Off

When the gear selector lever is moved to the Drive (D) position from the Neutral (N) position, and the internal combustion engine (ICE) is OFF, the following changes occur in the transmission's hydraulic and electrical systems in order to start the vehicle moving from a stopped position.

Pressure Control (PC) Solenoid 3

The PC solenoid 3 is energized (ON) allowing actuator feed limit fluid to enter the PCS 3 signal circuit. PCS 3 signal fluid is then routed through orifice #30 to the variable low and 1-2 reverse clutch regulator valve; through orifice #12 to the variable low and 1-2 reverse clutch boost valve; and to the shift solenoid valve- mode B.

Variable Low and 1-2 Reverse Clutch Regulator Valve

PCS 3 signal fluid, at the variable low and 1-2 reverse clutch regulator valve, opposes variable low and 1-2 reverse clutch regulator valve spring force and VL 12 reverse clutch feedback fluid pressure to regulate line or auxiliary line pressure into the VL 12 reverse clutch feed circuit.

Variable Low and 1-2 Reverse Clutch Boost Valve

PCS 3 signal fluid pressure acts on a differential area of the variable low and 1-2 reverse clutch boost valve, moving the valve against variable low and 1-2 reverse clutch boost valve spring force to regulate VL 12 reverse clutch feed fluid into the VL 12 reverse clutch feedback circuit. As PCS 3 signal fluid pressure is increased to a given value, the variable low and 1-2 reverse clutch boost valve opens the VL 1-2 reverse clutch feedback circuit to exhaust. This results in the variable low and 1-2 reverse clutch regulator valve moving to the full feed position, sending full VL 12 reverse clutch feed pressure (full line pressure) to the variable low and 1-2 reverse clutch.

Shift Solenoid Valve- Mode B

VL 12 reverse clutch feed fluid is routed to the shift solenoid valve- mode B, where it passes through the valve into the VL 12 reverse clutch circuit.

Variable Low and 1-2 Reverse Clutch Assembly

VL 12 reverse clutch fluid pressure enters the case assembly behind the variable low and 1-2 reverse clutch piston and moves the piston against spring force to apply the variable low and 1-2 reverse clutch plates.

Variable Low and 1-2 Reverse Clutch Accumulator

VL 12 reverse clutch fluid is also sent to the variable low and 1-2 reverse clutch accumulator assembly. VL 12 reverse clutch fluid moves the variable low and 1-2 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the variable low and 1-2 reverse clutch assembly.

Scheme 17

Drive Series Mode Engine On

When the gear selector lever is moved to the Drive (D) position from the Neutral (N) position, and the HPCM determines that operating conditions are appropriate, the internal combustion engine (ICE) is started, the auxiliary fluid pump is turned OFF, and the main fluid pump provides hydraulic fluid pressure (refer to Engine Start ). After Engine Start, the following changes would occur to the transmission's hydraulic and electrical systems in order to start the vehicle moving from a stopped position.

The 1-3 reverse clutch is applied for Engine Start, and remains applied for Reverse- Series Mode (Engine ON).

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is energized (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #18 to the 1-3 reverse clutch regulator valve.

Shift Solenoid 2

The shift solenoid 2 is energized (ON) allowing actuator feed limit fluid to enter the solenoid 2 signal fluid circuit. Solenoid 2 signal fluid is routed through orifice #21 to the shift solenoid valve- mode A. Solenoid 2 signal fluid is also routed to the variable hi and 2-3-4 clutch regulator valve, and to the 1-3 reverse clutch regulator valve.

1-3 Reverse Clutch Regulator Valve

PCS 4 signal fluid, at the 1-3 reverse clutch regulator valve, opposes 1-3 reverse clutch regulator valve spring force and 13 reverse clutch feedback fluid pressure to regulate line or auxiliary line pressure into the 13 reverse clutch/A cooling feed circuit.

#3 Ball Check Valve

13 reverse clutch feedback fluid unseats the #3 ball check valve, allowing excess pressure to pass into the actuator feed limit circuit. This helps to control clutch apply fluid pressure and clutch apply feel.

Shift Solenoid Valve - Mode A

13 reverse clutch/A cooling feed fluid passes through the shift solenoid valve- mode A and enters the 13 reverse clutch circuit.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid passes through the case and the transmission fluid pump cover into the 1-3 reverse clutch housing and moves the 1-3 reverse clutch piston against spring force to apply the 1-3 reverse clutch plates.

#1 Pressure Switch

Solenoid 2 signal fluid passes through the 1-3 reverse clutch regulator valve into the PS1 fluid passage. PS1 fluid opens the normally closed #1 pressure switch, signaling the TCM that the transmission is in Drive- Series Mode.

#3 Pressure Switch

Solenoid 2 signal fluid passes through the variable hi and 2-3-4 clutch regulator valve into the PS3 fluid passage. PS3 fluid opens the normally closed #3 pressure switch, signaling the TCM that the transmission is in Drive- Series Mode.

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is de-energized (OFF) allowing PCS 5 signal fluid to exhaust from the dampener bypass clutch valve.

Torque Dampener Clutch Assembly

Dampener clutch fluid exhausts from the torque dampener clutch assembly to the dampener bypass clutch valve allowing the torque dampener clutch to release.

Dampener Bypass Clutch Valve

Dampener bypass clutch valve spring force moves the dampener bypass clutch valve to the released position, allowing dampener clutch fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

Dampener clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

Variable Low and 1-2 Reverse Clutch Assembly

With the exception of the switch to line fluid pressure from the main fluid pump assembly, no other changes occur to the variable low and 1-2 reverse clutch fluid circuit and the variable low and 1-2 reverse clutch remains applied.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid is also sent to the 1-3 reverse clutch accumulator assembly. 13 reverse clutch fluid moves the 1-3 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the 1-3 reverse clutch assembly

Variable Low and 1-2 Reverse Clutch Accumulator

VL 12 reverse clutch fluid is also sent to the variable low and 1-2 reverse clutch accumulator assembly. VL 12 reverse clutch fluid moves the variable low and 1-2 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the variable low and 1-2 reverse clutch assembly.

Scheme 18

Drive Output Split Engine Off

When the gear selector lever is moved to the Drive (D) position from the Neutral (N) position, and the internal combustion engine (ICE) is OFF, the following changes occur in the transmission's hydraulic and electrical systems in order to start the vehicle moving from a stopped position.

Pressure Control (PC) Solenoid 2

The PC solenoid 2 is energized (ON) allowing actuator feed limit fluid to enter the PCS 2 signal circuit. PCS 2 signal fluid is then routed through orifice #20 to the variable hi and 2-3-4 clutch regulator valve.

Shift Solenoid 1

The shift solenoid 1 is energized (ON) allowing actuator feed limit fluid to enter the solenoid 1 signal fluid circuit. Solenoid 1 signal fluid is then routed through orifice #32 to the shift solenoid valve- mode B.

Variable Hi and 2-3-4 Clutch Regulator Valve

PCS 2 signal fluid, at the variable hi and 2-3-4 clutch regulator valve, opposes variable hi and 2-3-4 clutch regulator valve spring force and VH 234 clutch feedback fluid pressure to regulate line or auxiliary line pressure into the VH 234 clutch/B cooling feed circuit.

Variable Hi and 2-3-4 Clutch Boost Valve

PCS 2 signal fluid pressure acts on a differential area of the variable hi and 2-3-4 clutch boost valve, moving the valve against variable hi and 2-3-4 clutch boost valve spring force to regulate VH 234 clutch/B cooling feed fluid into the VH 234 clutch feedback circuit. As PCS 2 signal fluid pressure is increased to a given value, the variable hi and 2-3-4 clutch boost valve opens the VH 234 clutch feedback circuit to exhaust. This results in the variable hi and 2-3-4 clutch regulator valve moving to the full feed position, sending full VH 234 clutch feed pressure (full line pressure) to the variable hi and 2-3-4 clutch.

Shift Solenoid Valve- Mode A

VH 234 clutch/B cooling feed fluid passes through the shift solenoid valve- mode A into the VH 234 clutch feed fluid circuit and is routed to the shift solenoid valve- mode B.

Shift Solenoid Valve- Mode B

VH 234 clutch feed fluid passes through the shift solenoid valve- mode B into the VH 234 clutch circuit and is routed to the variable hi and 2-3-4 clutch assembly.

Variable Hi and 2-3-4 Clutch Assembly

VH 234 clutch fluid is directed to the variable hi and 2-3-4 clutch piston to apply the variable hi and 2-3-4 clutch plates and achieve Reverse- Output Split.

Pressure Control (PC) Solenoid 3

The PC solenoid 3 is de-energized (OFF) allowing PCS 3 signal fluid to exhaust from the variable low and 1-2 reverse clutch regulator valve; the variable low and 1-2 reverse clutch boost valve; and the shift solenoid valve-mode B.

Variable Low and 1-2 Reverse Clutch Assembly

VL 12 reverse clutch fluid exhausts from the variable low and 1-2 reverse clutch to the shift solenoid valve- mode B allowing the variable low and 1-2 reverse clutch to release.

Shift Solenoid Valve- Mode B

VL 12 reverse clutch fluid passes through the shift solenoid valve- mode B and into the exhaust backfill fluid circuit.

Variable Low and 1-2 Reverse Clutch Boost Valve

Variable low and 1-2 reverse clutch boost valve spring force moves the variable low and 1-2 reverse clutch boost valve to the released position, allowing VL 12 reverse clutch feedback fluid pressure to exhaust into the VL 12 reverse clutch feed circuit.

Variable Low and 1-2 Reverse Clutch Regulator Valve

Variable low and 1-2 reverse clutch regulator valve spring force moves the variable low and 1-2 reverse clutch regulator valve to the released position, allowing VL 12 reverse clutch feed fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

VL 12 reverse clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

Variable Hi and 2-3-4 Clutch Accumulator

VH 234 clutch fluid is also sent to the variable hi and 2-3-4 clutch accumulator assembly. VH 234 clutch fluid moves the variable hi and 2-3-4 clutch accumulator piston against accumulator spring force to cushion the apply of the variable hi and 2-3-4 clutch assembly.

Variable Low and 1-2 Reverse Clutch Accumulator

VL 12 reverse clutch fluid also exhausts from the variable low and 1-2 reverse clutch accumulator assembly. Accumulator spring force moves the variable low and 1-2 reverse clutch accumulator piston to the released position.

Scheme 19

Drive Output Split Engine On

When the gear selector lever is moved to the Drive (D) position from the Neutral (N) position, and the HPCM determines that operating conditions are appropriate, the internal combustion engine (ICE) is started, the auxiliary fluid pump is turned OFF, and the main fluid pump provides hydraulic fluid pressure (refer to Engine Start ). After Engine Start, the following changes would occur to the transmission's hydraulic and electrical systems in order to start the vehicle moving from a stopped position.

The 1-3 reverse clutch is applied for Engine Start, and remains applied for Reverse- Series Mode (Engine ON).

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is energized (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #18 to the 1-3 reverse clutch regulator valve.

Shift Solenoid 2

The shift solenoid 2 is energized (ON) allowing actuator feed limit fluid to enter the solenoid 2 signal fluid circuit. Solenoid 2 signal fluid is routed through orifice #21 to the shift solenoid valve- mode A. Solenoid 2 signal fluid is also routed to the variable hi and 2-3-4 clutch regulator valve, and to the 1-3 reverse clutch regulator valve.

1-3 Reverse Clutch Regulator Valve

PCS 4 signal fluid, at the 1-3 reverse clutch regulator valve, opposes 1-3 reverse clutch regulator valve spring force and 13 reverse clutch feedback fluid pressure to regulate line or auxiliary line pressure into the 13 reverse clutch/A cooling feed circuit.

#3 Ball Check Valve

13 reverse clutch feedback fluid unseats the #3 ball check valve, allowing excess pressure to pass into the actuator feed limit circuit. This helps to control clutch apply fluid pressure and clutch apply feel.

Shift Solenoid Valve- Mode A

13 reverse clutch/A cooling feed fluid passes through the shift solenoid valve- mode A and enters the 13 reverse clutch circuit.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid passes through the case and the transmission fluid pump cover into the 1-3 reverse clutch housing and moves the 1-3 reverse clutch piston against spring force to apply the 1-3 reverse clutch plates.

#1 Pressure Switch

Solenoid 2 signal fluid passes through the 1-3 reverse clutch regulator valve into the PS1 fluid passage. PS1 fluid opens the normally closed #1 pressure switch, signaling the TCM that the transmission is in Drive- Output Split.

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is de-energized (OFF) allowing PCS 5 signal fluid to exhaust from the dampener bypass clutch valve.

Torque Dampener Clutch Assembly

Dampener clutch fluid exhausts from the torque dampener clutch assembly to the dampener bypass clutch valve allowing the torque dampener clutch to release.

Dampener Bypass Clutch Valve

Dampener bypass clutch valve spring force moves the dampener bypass clutch valve to the released position, allowing dampener clutch fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

Dampener clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

Variable Hi and 2-3-4 Clutch Assembly

With the exception of the switch to line fluid pressure from the main fluid pump assembly, no other changes occur to the variable hi and 2-3-4 clutch fluid circuit and the variable hi and 2-3-4 clutch remains applied.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid is also sent to the 1-3 reverse clutch accumulator assembly. 13 reverse clutch fluid moves the 1-3 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the 1-3 reverse clutch assembly.

Variable Hi and 2-3-4 Clutch Accumulator

VH 234 clutch fluid is also sent to the variable hi and 2-3-4 clutch accumulator assembly. VH 234 clutch fluid moves the variable hi and 2-3-4 clutch accumulator piston against accumulator spring force to cushion the apply of the variable hi and 2-3-4 clutch assembly.

Scheme 20

Power Off Default

If the transmission experiences an electrical component malfunction, all solenoids will default to their normal state. The transmission will operate in Default whenever the gear selector lever is a forward range. The transmission will remain in this default state until the condition is corrected. Reverse (R) range can also still be selected. This default action enables the vehicle to be safely driven to a service center.

Variable Low and 1-2 Reverse Clutch Applied or Remains Applied

When an electrical malfunction occurs, the PC solenoid 3 defaults to its normally high state (ON). Depending on the operating mode of the transmission at the time of the malfunction, the variable low and 1-2 reverse clutch is either applied or remains applied.

Pressure Control (PC) Solenoid 3

The PC solenoid 3 defaults to its normally high state (ON) allowing actuator feed limit fluid to enter the PCS 3 signal circuit. PCS 3 signal fluid is then routed through orifice #30 to the variable low and 1-2 reverse clutch regulator valve; through orifice #12 to the variable low and 1-2 reverse clutch boost valve; and to the shift solenoid valve-mode B.

Variable Low and 1-2 Reverse Clutch Boost Valve

PCS 3 signal fluid pressure acts on a differential area of the variable low and 1-2 reverse clutch boost valve, moving the valve against variable low and 1-2 reverse clutch boost valve spring force to block VL 12 reverse clutch feed fluid from entering the VL 12 reverse clutch feedback circuit, and opening the VL 12 reverse clutch feedback circuit to exhaust. This results in the variable low and 1-2 reverse clutch regulator valve moving to the full feed position, sending full VL 12 reverse clutch feed pressure (full line pressure) to the variable low and 1-2 reverse clutch.

Variable Low and 1-2 Reverse Clutch Regulator Valve

PCS 3 signal fluid moves the variable low and 1-2 reverse clutch regulator valve, against variable low and 1-2 reverse clutch regulator valve spring force, to the applied position. This allows line or auxiliary line fluid to pass through the valve into the VL 12 reverse clutch feed circuit.

Shift Solenoid Valve - Mode B

VL 12 reverse clutch feed fluid is routed to the shift solenoid valve- mode B, where it passes through the valve into the VL 12 reverse clutch circuit.

Variable Low and 1-2 Reverse Clutch Assembly

VL 12 reverse clutch fluid pressure enters the case assembly behind the variable low and 1-2 reverse clutch piston and moves the piston against spring force to apply the variable low and 1-2 reverse clutch plates.

The normally low pressure control solenoid 4 and the normally closed shift solenoid 2 default to their normal states (OFF), and the 1-3 reverse clutch is released if it was applied at the time of the malfunction.

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is commanded OFF, allowing PCS 4 signal fluid to exhaust from the 1-3 reverse clutch regulator valve.

Shift Solenoid 2

The shift solenoid 2 is commanded OFF, allowing solenoid 2 signal fluid to exhaust. When solenoid 2 signal fluid exhausts, the shift solenoid valve- mode A moves to the released position.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid pressure is exhausted from the 1-3 reverse clutch housing assembly, allowing 1-3 reverse clutch spring force to move the 1-3 reverse clutch piston and release the 1-3 reverse clutch plates.

Shift Solenoid Valve- Mode A

13 reverse clutch fluid pressure exhausts at the shift solenoid valve- mode A.

#3 Ball Check Valve

13 reverse clutch feedback fluid pressure exhausts into the 13 reverse clutch/A cooling feed circuit, allowing actuator feed limit fluid to seat the ball.

1-3 Reverse Clutch Regulator Valve

1-3 reverse clutch regulator valve spring force moves the 1-3 reverse clutch regulator valve to the released position, allowing 13 reverse clutch/A cooling feed fluid pressure to exhaust.

The normally closed shift solenoid 1 and shift solenoid 2 default to their normal states (OFF), and the variable hi and 2-3-4 clutch is released if it was applied at the time of the malfunction.

Pressure Control (PC) Solenoid 2

The PC solenoid 2 is commanded OFF, allowing PCS 2 signal fluid to exhaust from the variable hi and 2-3-4 clutch regulator valve and the variable hi and 2-3-4 clutch boost valve.

Variable Hi and 2-3-4 Clutch Assembly

VH 234 clutch fluid pressure is exhausted from the case assembly, allowing variable hi and 2-3-4 clutch spring force to move the variable hi and 2-3-4 clutch piston and release the variable hi and 2-3-4 clutch plates.

Shift Solenoid Valve- Mode B

Exhausting VH 234 clutch fluid pressure passes through the shift solenoid valve- mode B into the VH 234 clutch feed circuit.

Shift Solenoid Valve- Mode A

VH 234 clutch feed fluid pressure exhausts at the shift solenoid valve- mode A.

Variable Hi and 2-3-4 Clutch Regulator Valve

Variable hi and 2-3-4 clutch regulator valve spring force moves the variable hi and 2-3-4 clutch regulator valve to the released position, allowing VH 234 clutch/B cooling feed fluid pressure to exhaust.

If the torque dampener clutch is applied when an electrical malfunction occurs, the clutch will release when the PC solenoid 5 defaults to its normally low state (OFF).

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is de-energized (OFF) allowing PCS 5 signal fluid to exhaust from the dampener bypass clutch valve.

Torque Dampener Clutch Assembly

Dampener clutch fluid exhausts from the torque dampener clutch assembly to the dampener bypass clutch valve allowing the torque dampener clutch to release.

Dampener Bypass Clutch Valve

Dampener bypass clutch valve spring force moves the dampener bypass clutch valve to the released position, allowing dampener clutch fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

Dampener clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

Variable Low and 1-2 Reverse Clutch Accumulator

VL 12 reverse clutch fluid is also sent to the variable low and 1-2 reverse clutch accumulator assembly. VL 12 reverse clutch fluid moves the variable low and 1-2 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the variable low and reverse clutch assembly.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid also exhausts from the 1-3 reverse clutch accumulator assembly. Accumulator spring force moves the 1-3 reverse clutch accumulator piston to the released position.

Variable Hi and 2-3-4 Clutch Accumulator

VH 234 clutch fluid also exhausts from the variable hi and 2-3-4 clutch accumulator assembly. Accumulator spring force moves the variable hi and 2-3-4 clutch accumulator piston to the released position.

Scheme 21

Scheme 22

Scheme 23

Scheme 24

Scheme 25

Scheme 26

Scheme 27

Scheme 28

Scheme 29

Scheme 30

Scheme 31

Scheme 32

Scheme 33

Scheme 34

Scheme 35

Scheme 36

Scheme 37

Scheme 38

Scheme 39

See also:
• Drive Motor Generator Power Inverter Module Description and Operation
• Electronic Component Description
• Engine Start