Automatic Transmission - 4t65-e - Description and Operation Chevrolet Impala IX

How to Use This Service information

This service information provides the following information

1. General diagnosis information on transmissions
2. Procedures for diagnosing the Hydra-matic transmission

When you diagnose any condition of the Hydra-matic transmission, begin with a Diagnostic Starting Point. This procedure indicates the proper path of diagnosing the transmission by describing the basic checks. This procedure will then refer you to the locations of specific checks. After you have determined the cause of a condition, refer to Repair Instructions for repair procedures.

Basic Knowledge

You must be familiar with some basic electronics in order to use this section of the service information. You should also be able to use the following special tools

1. A digital multimeter (DMM)
2. A circuit tester
3. Jumper wires or leads
4. A line pressure gauge set

Scheme 6

Transmission General Description

The 4T65-E is a fully automatic front wheel drive electronically controlled transmission. The 4T65-E provides four forward ranges including overdrive. The PCM controls shift points by means of two shift solenoids. A vane-type oil pump supplies the oil pressure. The PCM regulates oil pressure by means of a pressure control solenoid valve.

All vehicles equipped with a 4T65-E transmission have an electronically controlled capacity clutch (ECCC) system. In the ECCC system, the pressure plate does not fully lock to the torque converter cover. It is instead, precisely controlled to maintain a small amount of slippage between the engine and the turbine, reducing driveline torsional disturbances.

You can operate the transmission in any one of the following seven modes

1. P - Park position prevents the vehicle from rolling either forward or backward. For safety reasons, use the parking brake in addition to the park position.
2. R - Reverse allows the vehicle to be operated in a rearward direction.
3. N - Neutral allows the engine to be started and operated while driving the vehicle. If necessary, you may select this position in order to restart the engine with the vehicle moving.
4. D - Overdrive is used for all normal driving conditions. Overdrive provides four gear ratios plus a converter clutch operation. Depress the accelerator in order to downshift for safe passing.
5. 3 - Drive position is used for city traffic and hilly terrain. Drive provides three gear ranges and drive range prevents the transmission from operating in fourth gear. Depress the accelerator in order to downshift.
6. 2 - Manual Second provides two gear ratios under most operating conditions. Manual Second provides acceleration and engine braking. Select this range at any vehicle speed, but the transmission will not downshift into Second gear until the vehicle speed drops below approximately 100 km/h (62 mph)
7. 1 - Manual Lo provides maximum engine braking. You may also select this range at any vehicle speed, but the transmission will not downshift into First gear until the vehicle speed drops below approximately 60 km/h (37 mph).

Transmission Component and System Description

The mechanical components of this unit are as follows

1. A torque converter with an electronically controlled capacity clutch (ECCC) This transmission is equipped with an ECCC. The pressure plate does not fully lock to the torque converter cover. Instead, the pressure plate maintains a small amount of slippage, about 20 RPM, in SECOND, THIRD and FOURTH gears, depending on the vehicle application. ECCC was developed to reduce the possibility of noise, vibration or chuggle caused by torque converter clutch (TCC) apply. Typical apply speeds are 49-52 km/h (30-32 mph) in THIRD gear and 65-73 km/h (40-45 mph) in FOURTH gear. Full lockup is available at highway speeds on some applications.
2. A drive link assembly
3. 4 multiple disk clutch assemblies: Input, Second, Third and Fourth
4. 3 friction bands: Forward band, 2/1 band and Reverse band
5. 2 planetary gear sets: Input and Reaction
6. 3 one-way clutches: a roller clutch (1-2 support) and 2 sprag clutches (Third and Input)
7. A final drive and differential assembly
8. A control valve assembly
9. A vane type oil pump

The electrical components of this unit are as follows

1. 2 shift solenoid valves
2. A torque converter clutch pulse width modulation (TCC PWM) solenoid valve
3. A pressure control (PC) solenoid valve
4. An automatic transmission fluid temperature (TFT) sensor
5. 2 speed sensors: input shaft and vehicle speed sensors
6. An automatic transmission fluid pressure (TFP) manual valve position switch
7. Either an internal mode switch (IMS) or an externally-mounted transmission range (TR) switch.
8. An automatic transmission (A/T) wiring harness assembly

For more information, refer to Electronic Component Description .

Transmission Adaptive Functions

The 4T65-E transmission uses a line pressure control system, that has the ability to adapt line pressure to compensate for normal wear of the following parts

1. The clutch fiber plates
2. The springs and seals
3. The apply bands

The PCM maintains information for the following transmission adaptive systems

Upshift Adapts (1-2, 2-3 and 3-4)

The PCM monitors the automatic transmission input speed sensor (ISS) and the vehicle speed sensor (VSS) in order to determine when an upshift has started and completed. The PCM measures the time for the upshift. If the upshift time is longer than a calibrated value, then the PCM will adjust the current to the pressure control (PC) solenoid valve to increase the line pressure for the next shift in the same torque range. If the upshift time is shorter than the calibrated value, then the PCM will decrease the line pressure for the next shift in the same torque range.

Steady State Adapts

The PCM monitors the ISS and the VSS after an upshift in order to determine the amount of clutch slippage. If excessive slippage is detected, then the PCM will adjust the current to the PC solenoid valve in order to increase the line pressure to maintain the proper gear ratio for the commanded gear.

The TAP information is divided into 13 units, called cells. The cells are numbered 4 through 16. Each cell represents a given torque range. TAP cell 4 is the lowest adaptable torque range and TAP cell 16 is the highest adaptable torque range. It is normal for TAP cell values to display zero or negative numbers. This indicates that the PCM has adjusted line pressure at or below the calibrated base pressure.

Clearing Transmission Adaptive Pressure (TAP)

Updating TAP information is a learning function of the PCM designed to maintain acceptable shift times. It is not recommended that TAP information be reset unless one of the following repairs has been made

1. Transmission overhaul or replacement
2. Repair or replacement of an apply or release component - clutch, band, piston, servo
3. Repair or replacement of a component or assembly which directly affects line pressure

Resetting the TAP values using a scan tool will erase all learned values in all cells. As a result, the PCM will need to relearn TAP values. Transmission performance may be affected as new TAPs are learned. The PCM must also relearn TAP values when the PCM or the transmission is replaced.

Scheme 7

The vehicle speed sensor (VSS) is a magnetic inductive pickup that relays vehicle speed information to the PCM. The PCM uses this information in order to control shift timing, line pressure, and TCC apply and release.

The VSS mounts in the case extension at the vehicle speed sensor reluctor wheel, which is pressed onto the final drive carrier assembly. An air gap of 0.27-1.57 mm (0.011-0.062 in) occurs between the sensor and the teeth on the vehicle speed sensor reluctor wheel as the final drive carrier assembly rotates.

The sensor consists of a permanent magnet surrounded by a coil of wire. As the vehicle speed sensor reluctor wheel on the final drive carrier assembly rotates, an AC signal is produced by the VSS. This AC signal consists of a voltage and frequency that changes based on vehicle speed. The PCM uses the frequency portion of this signal to determine vehicle speed. Higher vehicle speeds induce a higher frequency and a higher voltage measurement at the sensor. The voltage portion of the signal is used in diagnostic procedures.

Sensor resistance should measure between 1,650-2,200 ohms at 20°C (68°F). Output voltage will vary with vehicle speed from a minimum of 0.5 volts AC at 100 RPM to 200 volts at 6,000 RPM.

Scheme 8

The automatic transmission input speed sensor (ISS) is a magnetic inductive pickup that relays turbine shaft speed information to the PCM. The PCM uses ISS information in order to control line pressure, transmission shift patterns and TCC apply and release. This information is also used in order to calculate the appropriate operating gear ratios and TCC slippage.

The ISS mounts in the case cover, next to the reluctor wheel assembly. An air gap of 0.08-2.12 mm (0.0032-0.0834 in) occurs between the sensor and the teeth on the speed sensor reluctor wheel as the drive sprocket rotates. The speed sensor reluctor wheel is secured to and turns with the drive sprocket by the tangs on the drive sprocket forward thrust washer.

The sensor consists of a permanent magnet surrounded by a coil of wire. As the turbine shaft rotates the speed sensor reluctor wheel and the drive sprocket, an AC signal is produced by the ISS. This AC signal consists of a voltage and frequency that changes based on vehicle speed. The PCM uses the frequency portion of this signal to determine input shaft speed. Higher input shaft speeds induce a higher frequency and a higher voltage measurement at the sensor. The voltage portion of the signal is used in diagnostic procedures.

Sensor resistance should measure between 820-1020 ohms at 20°C (68°F). Output voltage will vary with the vehicle speed from a minimum of 0.5 volts AC at 300 RPM to 200 volts at 6,000 RPM.

Scheme 9

The shift solenoid valves are two identical, normally open, electronic exhaust valves that control upshifts and downshifts in all forward gear ranges. These shift solenoid valves work together in a combination of ON and OFF sequences in order to control the positions of the 1-2 and 2-3 shift valve trains. The PCM monitors numerous inputs in order to determine the appropriate solenoid state combination and the transmission gear for the vehicle operating conditions.

The PCM energizes the shift solenoids by providing a ground to the solenoid's electrical circuit. This sends a current through the coil winding of the solenoid, thereby creating a magnetic field. The magnetic field repels the plunger inside the solenoid. This seats the solenoid metering ball against the fluid inlet port. This action prevents the exhaust of fluid through the solenoid and provides an increase in fluid pressure at the end of the shift valves. This fluid pressure initiates an upshift by moving the shift valves. Refer to the oil flow diagrams for a complete description of the hydraulic control of the shift valves for each gear range.

Shift solenoid resistance should measure between 19-24 ohms when measured at 20°C (68°F) and between 24-31 ohms when measured at 88°C (190°F).

The shift solenoid valves should energize when the voltage is greater than 7.5 volts. The shift solenoid valves should de-energize when the voltage is less than one volt.

Scheme 10

The pressure control (PC) solenoid valve is a precision electronic pressure regulator that controls transmission line pressure based on current flow through its coil windings. As current flow is increased, the magnetic field which is produced by the coil moves the solenoid's plunger further away from the exhaust port. Opening the exhaust port decreases the output fluid pressure, which is regulated by the PC solenoid valve. This ultimately decreases line pressure. The PCM controls the PC solenoid valve based upon various inputs including throttle position, fluid temperature, MAP sensor, and gear state.

The PCM controls the PC solenoid valve on a positive duty cycle at a fixed frequency of 585 Hz (cycles per second). Duty cycle is defined as the percentage of time when current flows through the solenoid coil during each cycle. A higher duty cycle provides a greater current flow through the solenoid. The high (positive) side of the PC solenoid valve electrical circuit at the PCM controls the PC solenoid valve operation. The PCM provides a ground path for the circuit, monitors average current, and continuously varies the PC solenoid valve duty cycle in order to maintain the correct average current flowing through the PC solenoid valve.

The PC solenoid valve resistance should measure between 3-5 ohms when measured at 20°C (68°F).

Scheme 11

The TCC PWM solenoid valve is a normally closed (hydraulically), pulse width modulation (PWM) solenoid which is used to control the apply and release of the converter clutch. The PCM operates the solenoid with a negative duty cycle at a fixed frequency of 32 Hz in order to control the rate of TCC apply/release. The solenoid's ability to ramp the TCC apply and release pressures results in smoother TCC operation.

When the vehicle's operating conditions are appropriate to apply the TCC, the PCM immediately increases the duty cycle to approximately 22 percent. The PCM then ramps the duty cycle up to a maximum of 98 percent in order to achieve full TCC apply pressure. The rate at which the PCM increases the duty cycle controls the TCC apply. Similarly, the PCM also ramps down the TCC solenoid duty cycle in order to control TCC release.

Some operating conditions prevent or enable TCC apply under various conditions. Refer to Automatic Transmission Fluid Temperature Sensor in this section. Also, if the PCM receives a zero voltage signal from the TCC brake switch, signaling that the brake pedal has been depressed, the PCM immediately releases the TCC.

TCC duty cycle for ECCC equipped vehicles is 22 percent for minimum apply pressure and 43 percent for maximum apply pressure. The TCC PWM solenoid valve will typically be 40-60 percent at full apply. Your results may vary.

The TCC PWM solenoid valve resistance should measure 10-12 ohms when measured at 20°C (68°F) and 13-15 ohms when measured at 88°C (190°F).

Scheme 12

The automatic transmission fluid pressure (TFP) switch is attached to the valve body and consists of one fluid pressure switch that monitors TCC release pressure. This switch is used as a diagnostic tool to confirm that the TCC is actually OFF when it has been commanded OFF by the PCM.

The TCC release switch is a normally-closed pressure switch. A normally-closed switch allows current to flow from the positive contact through the switch to ground when no fluid is present. Fluid pressure moves the diaphragm to disconnect the positive and ground contacts, opening the switch and stopping current flow. This change in switch state electronically signals the PCM that the TCC is released.

Scheme 13

The lever assembly-manual shaft detent with internal mode switch (IMS) is a sliding contact electrical switch assembly that corresponds to the PRNDL position selected. Each of the PRNDL positions has a unique ground pattern on four wires from the PCM.

The assembly consists of two major components

1. The internal mode switch that consists of: The housing (1), which makes up the stationary contacts. The insulator (2), which makes up the moving contacts and is secured on the detent lever (4).
2. The lever assembly which consists of: The manual shaft (3) The detent lever (4)

The range detection is accomplished by securing the moving contacts to the detent lever. When the driver selects a PRNDL position, the detent lever inside the transmission rotates. This rotates the insulator which in turn grounds the four wires in a unique pattern for each gear selection, corresponding to the PRNDL position selected. The IMS is electrically connected by five wires (four of which the PCM supplies voltage to and one wire that is a common ground) to the transmission pass through connector.

Scheme 14

The automatic transmission fluid temperature (TFT) sensor is a negative temperature coefficient thermistor (temperature sensitive resistor) that provides information to the PCM regarding the transmission fluid temperature. The TFT sensor clips on to the valve body and is replaced as a separate component and not as a part of the AT wiring harness assembly. The TFT sensor monitors non-pressurized fluid in the sump in order to determine the operating temperature of the transmission fluid.

The internal electrical resistance of the sensor varies in relation to the operating temperature of the transmission fluid. The PCM sends a 5 volt reference signal to the TFT sensor and the PCM measures the voltage drop in the electrical circuit. A lower fluid temperature creates a higher resistance in the TFT sensor, which produces a higher voltage signal.

The PCM uses this input in order to help determine the proper line pressure, shift schedules and TCC apply. When the transmission fluid temperature reaches 130°C (266°F), the PCM enters Hot Mode. Above this temperature the PCM modifies the transmission shift schedules and the TCC apply in an attempt to reduce the fluid temperature by reducing the transmission heat generation. During Hot Mode the PCM applies the TCC at all times in third and fourth gears. Also, the PCM performs the 2-3 and the 3-4 shifts earlier in order to help reduce fluid heat generation.

The PCM stays in Hot Mode until the temperature drops below 120°C (248°F).

Scheme 15

The transmission electrical connector is an important part of the transmission operating system. Any interference with the electrical connection can cause the transmission to set Diagnostic Trouble Codes (DTCs) or affect proper operation.

The following items can affect the electrical connection

1. Bent pins in the connector from rough handling during connection and disconnection
2. Wires that are within either the internal or external wiring harness which back away from the pins or become uncrimped
3. Dirt contamination entering the connector when disconnected
4. Pins in the internal wiring connector backing out of the connector or pushed out of the connector during reconnection
5. Excessive transmission fluid leaking into the connector, wicking up into the external wiring harness and degrading the wire insulation
6. Moisture intrusion in the connector
7. Low pin retention in the external connector from excessive connection and disconnection of the wiring connector assembly
8. Pin corrosion from contamination
9. Damaged connector assembly

Remember the following points

1. In order to remove the connector, squeeze the two tabs toward each other and pull straight up without pulling by the wires.
2. Limit twisting or wiggling the connector during removal. Bent pins can occur.
3. Do not pry the connector off with a screwdriver or other tool.
4. Visually inspect the seals to ensure that they are not damaged during handling.
5. In order to reinstall the external wiring connector, first orient the pins by lining up the arrows on each half of the connector. Push the connector straight down into the transmission without twisting or angling the mating parts.
6. The connector should click into place with a positive feel and/or noise.
7. Whenever the transmission external wiring connector is disconnected from the internal harness and the engine is operating, DTCs will set. Clear these DTCs after reconnecting the external connector.

Park or Neutral - Engine Running (Park)

When the gear selector lever is in the PARK (P) position and the engine is running, fluid is drawn into the oil pump and line pressure is then directed to the following control devices

Pressure Regulator Valve (313)

Regulates pump output (line pressure) in response to torque signal fluid pressure acting on the boost valve, spring force and line pressure acting on the end of the valve. Line pressure is directed to the manual valve, 3 accumulator valves, torque signal regulator valve, pressure relief valve, TCC regulator valve, #10 ball check valve and 2-3 shift valve, 3-2 manual downshift valve, 3-4 shift valve, 2-3 shift solenoid valve, #3 ball check valve and input clutch, and actuator feed limit valve.

Actuator Feed Limit Valve (414)

Line pressure is routed to the valve and limited to a maximum pressure as it passes through the valve and enters the actuator feed circuit. Actuator feed is then routed to the pressure control solenoid valve and into the 1-2, 3-4 shift solenoid valve.

Pressure Control (PC) Solenoid Valve (322)

Controlled by the PCM, the PC solenoid valve regulates filtered actuator feed pressure entering the torque signal circuit. Torque signal fluid is then routed to the pressure regulator valve, the 1-2, 2-3 and 3-4 accumulator valves.

Torque Signal Regulator Valve (321)

Regulates line pressure into the torque signal fluid circuit. This regulation is controlled by filtered actuator feed fluid pressure from the PC solenoid valve.

Line Pressure Relief Valve (324)

Exhausts line pressure above 1,690-2,480 kPa (450-360 psi).

Manual Valve (404)

The manual valve is moved to the NEUTRAL position and blocks line pressure from entering the Reverse fluid circuit. The reverse fluid circuit is opened to an exhaust at the manual valve.

Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly (34)

The automatic transmission fluid pressure (TFP) switch is attached to the valve body and consists of one fluid pressure switch that monitors TCC release pressure. This switch is used as a diagnostic tool to confirm that the TCC is actually off when it has been commanded off by the PCM.

The TCC release switch is a normally closed pressure switch. A normally closed switch allows current to flow from the positive contact through the switch to ground when no fluid is present. Fluid pressure moves the diaphragm to disconnect the positive and ground contacts, opening the switch and stopping current flow. This change in switch state electronically signals the PCM that the TCC is released.

1-2, 3-4 Shift Solenoid Valve (315A)

Controlled by the powertrain control module (PCM), the 1-2, 3-4 shift solenoid (SS) valve is energized (On) in PARK range. Actuator feed pressure moves the 1-2 shift valve (318) against spring pressure and directs line fluid into the 1-2, 3-4 signal passage. 1-2, 3-4 signal fluid is then directed to the 3-4 shift valve (362).

2-3 Shift Solenoid Valve (315B)

Controlled by the powertrain control module (PCM), the 2-3 shift solenoid (SS) valve is energized (On) in PARK range and directs line pressure into the 2-3 signal passage. 2-3 signal fluid directed to the 4-3 manual downshift valve (360) and moves the valve against spring pressure, and also the 3-2 manual downshift valve (356).

1-2 Shift Valve (318)

1-2 signal fluid pressure holds the valve in the downshifted position against spring force.

2-3 Shift Valve (357)

In PARK range, line pressure passes through the 2-3 shift valve (357) and line pressure feeds the input clutch feed passage. Line pressure then passes through the 3-4 shift valve (362) and around the #3 ball check valve (372), located in the case cover) in order to apply the input clutch. Although the input clutch is applied and the input sprag is holding, these conditions are not effective because neither the forward band assembly (688) nor the reverse band assembly (615) is applied.

1-2, 2-3 and 3-4 Accumulator Valves (350, 344, 341)

Line pressure is regulated into accumulator fluid pressure. This regulation is basically controlled by torque signal fluid pressure acting on the end of the valve.

1-2, 2-3 and 3-4 Accumulator Assemblies

Accumulator fluid is routed to each of the accumulator assemblies in preparation for upshifts. The fluid routed to the 1-2, 2-3 and 3-4 accumulators is orificed.

Pressure Regulator Valve (313) (Torque Converter/Cooler and Lube Circuits)

Line pressure at the valve enters the converter feed circuit which is then routed to the TCC control valve.

TCC Control Valve (335)

Spring pressure holds the valve in the released position. Converter feed fluid is directed to the release circuit. Release fluid seats #1 ball check valve and feeds the TCC blow-off. Release fluid feeds the TCC on the cover side of the pressure plate, exits the TCC through the apply circuit, then feeds the cooler circuit at the TCC control valve. Cooler fluid passes through the ball check valve, through the cooler, then returns to the transmission and feeds the rear lube circuit. A front lube circuit is fed from orificed line pressure.

Scheme 16

Park or Neutral - Engine Running (Neutral)

When the gear selector lever is moved from the REVERSE position to the NEUTRAL position the following changes occur to the hydraulic and electrical systems.

The manual valve is moved to the NEUTRAL position and blocks line pressure from entering the Reverse fluid circuit. The reverse fluid circuit is opened to an exhaust at the manual valve.

Reverse Band Assembly (615)

Reverse fluid exhausts from the reverse servo, the #5 ball check valve unseats, allowing reverse servo fluid to quickly exhaust at the manual valve, and the reverse band releases, shifting the transmission into NEUTRAL.

Line pressure at the valve enters the converter feed circuit which is then routed to the TCC control valve.

Spring pressure holds the valve in the released position. Converter feed fluid is directed to the release circuit. Release fluid seats #1 ball check valve and feeds the TCC blow-off. Release fluid feeds the TCC on the cover side of the pressure plate, exits the TCC through the apply circuit, then feeds the cooler circuit at the TCC control valve. Cooler fluid passes through the ball check valve, through the cooler, then returns to the transmission and feeds the rear lube circuit. A front lube circuit is fed from orificed line pressure.

Scheme 17

Reverse

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.

Increases (or decreases) in line pressure is primarily influenced by changes in the throttle position as a result of the changing operating conditions of the vehicle.

Is moved manually to the right through the gear selector lever and allows line pressure to enter the reverse fluid passage through the PRN fluid passage.

Number 5 Ball Check Valve (373)

Located in the control valve body, (300), it blocks the reverse servo feed passage forcing reverse fluid through an orifice in the spacer plate (370) into the reverse servo passage. When the manual valve (404) is moved out of reverse, the ball check valve unseats allowing reverse servo fluid to exhaust through the ball seat instead of through the orifice.

Reverse Servo Assembly (39-40)

Applies the reverse band (615) in response to reverse servo fluid pressure feeding into the servo cover (40) side of the reverse servo piston (44).

Wraps around the second clutch housing (617) and holds the input carrier (672), through the reverse reaction drum (669), allowing the vehicle to move in reverse.

Input Clutch

Remains applied from PARK to REVERSE and becomes effective as the reverse band applies. The input sprag holds at this time.

Line pressure at the valve enters the converter feed circuit which is then routed to the TCC control valve.

Spring pressure holds the valve in the released position. Converter feed fluid is directed to the release circuit. Release fluid seats #1 ball check valve and feeds the TCC blow-off. Release fluid feeds the TCC on the cover side of the pressure plate, exits the TCC through the apply circuit, then feeds the cooler circuit at the TCC control valve. Cooler fluid passes through the ball check valve, through the cooler, then returns to the transmission and feeds the rear lube circuit. A front lube circuit is fed from orificed line pressure.

Scheme 18

Overdrive Range, First Gear

When the gear selector lever is moved to the Overdrive (D) position from the NEUTRAL (N) position the following changes occur to shift the transmission into Overdrive Range - First Gear.

Is moved by the gear selector lever and allows line pressure to enter the D4 passage.

Number 6 Ball Check Valve (372)

Located in the control valve body (300), blocks forward servo apply passage forcing D4 pressure to the forward servo boost valve (367), the forward servo feed orifice on the spacer plate (370). When the manual valve (404) is moved from DRIVE to PARK or NEUTRAL, the ball check valve unseats to allow for a quick exhaust of servo apply fluid and release of the forward band assembly (688).

Forward Servo Assembly (15-22)

Applies and holds the forward band (688) during all forward gear drive ranges.

Forward Band Assembly (688)

Wraps around and holds the 1-2 support outer race (687) during all forward gear drive ranges.

1-2 Shift Solenoid (SS) Valve (315A)

Energized (ON) by the PCM, high pressure in the 1-2, 3-4 signal fluid circuit holds the 12 shift valve in the downshifted position. 1-2, 3-4 signal fluid also is routed to the 3-4 shift valve, but is not effective.

2-3 Shift Solenoid (SS) Valve (315B)

Energized (ON) by the PCM, high pressure in the 2-3 signal fluid circuit holds the 2-3 and 3-4 shift valves in the downshifted position.

Remains applied from NEUTRAL to DRIVE and becomes effective as the forward band applies. The input sprag holds at this time.

1-2 Support Roller Clutch

The 1-2 support roller clutch holds when the forward band is applied.

Scheme 19

Overdrive Range, Second Gear

As the speed of the vehicle increases, the powertrain control module (PCM) receives input signals from various engine and transmission sensors. The PCM uses this data to de-energize 1-2, 3-4 shift solenoid valve in order to shift the transmission into second gear at the appropriate time.

1-2, 3-4 Shift Solenoid (SS) Valve (315A)

De-energized (OFF) by the PCM, it exhausts 1-2, 3-4 signal fluid through the solenoid thereby creating a low 1-2, 3-4 signal fluid pressure in the circuit. Low 1-2, 3-4 signal fluid pressure allows the 1-2 shift valve to move to the upshifted position.

With the 1-2, 3-4 SS valve OFF, spring pressure moves the valve allowing D4 pressure to enter the 2nd fluid passage directing 2nd fluid to the Number 2 ball check valve.

Number 2 Ball Check Valve (372)

Located in the case cover (400), 2nd fluid seats the ball check valve and is forced through an orifice into the 2nd clutch passage to apply the 2nd clutch.

Second Clutch

2nd clutch fluid pressure applies the Second clutch to shift the transmission into Overdrive Range - Second gear.

Remains applied, but is now ineffective.

Input Sprag Clutch

Overruns as the second clutch applies.

Forward Band

Remains applied.

Continues to hold while the forward band is applied.

1-2 Accumulator

2nd clutch fluid is also routed to the 1-2 accumulator piston. 2nd Clutch fluid pressure, in addition to 1-2 assist spring force, moves the piston against spring force and 1-2 accumulator feed fluid pressure. This action absorbs initial 2nd clutch fluid pressure to cushion the second clutch apply. The movement of the 1-2 accumulator piston forces some accumulator fluid out of the accumulator.

1-2 Accumulator Valve

1-2 accumulator feed fluid forced from the 1-2 accumulator is routed back to the 1-2 accumulator valve. This pressure forces the 1-2 accumulator valve against spring force and the torque signal fluid pressure to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the second clutch apply.

TCC Control Pulse Width Modulated (PWM) Solenoid Valve

2nd fluid is routed to the TCC control PWM solenoid. Under normal operating conditions the TCC control PWM solenoid is OFF in Second gear and blocks 2nd fluid from entering the TCC signal fluid circuit.

Torque Converter Clutch

With the TCC control PWM solenoid OFF the converter clutch is released in Second gear. Under normal operating conditions the TCC is released in Second gear. However, TCC apply could vary depending on vehicle application and may be calibrated to apply in Overdrive Range - Second Gear.

Transmission Fluid Pressure (TFP) Manual Valve Position Switch

Release fluid pressure routed to the TFP manual valve position switch signals the PCM that the TCC is released.

Scheme 20

Overdrive Range, Third Gear - Torque Converter Clutch Not Applied

As the speed of the vehicle increases, the powertrain control module (PCM) receives input signals from various engine and transmission sensors. The PCM uses this data to energize the 2-3 shift solenoid (SS) valve in order to shift the transmission into third gear at the appropriate time.

2-3 Shift Solenoid (SS) Valve (315)

De-energizes, allowing 2-3 signal fluid to exhaust through the solenoid. Spring pressure forces the 4-3 manual downshift valve (360) to move while line pressure moves the 2-3 shift valve (357) and 3-2 manual downshift valve (356).

Number 9 Ball Check Valve (372)

Located in the control valve body (300), forces 3rd fluid through a feed orifice and into the 3rd clutch passage.

Number 4 Ball Check Valve (372)

Located in the case cover (400), directs 3rd clutch fluid into the 3rd clutch/lo-1st passage to apply the 3rd clutch.

When shifted, allows D4 fluid to enter the 3rd passage to stroke the 2-3 accumulator piston (136) and apply the 3rd clutch. The 2-3 shift valve also allows input clutch apply fluid to exhaust into the D3 passage and out at the manual valve (404). And provides 2-3 off signal fluid to the 1-2 shift valve.

Third Clutch

3rd clutch/lo-1st fluid pressure applies the third clutch to shift the transmission into Third gear.

Third Roller Clutch

Holds as third clutch applies.

In third gear, the input clutch is released allowing input clutch apply fluid to exhaust through the 3-4 shift valve (362) into the input clutch feed passage. At the 2-3 shift valve (357), exhausting input clutch apply fluid is directed into the D3 passage and out the manual valve (404).

Remains applied, but is ineffective.

Overruns as third clutch is applied.

2-3 Accumulator

Third clutch feed fluid is also routed to the 2-3 accumulator piston. This fluid pressure moves the piston against spring force and 2-3 accumulator feed fluid pressure. This action absorbs initial third clutch fluid pressure to cushion the third clutch apply. The movement of the 2-3 accumulator piston forces some accumulator fluid out of the accumulator.

2-3 Accumulator Valve

Excess 2-3 accumulator feed fluid is routed back to the 2-3 accumulator valve. This fluid pressure moves the accumulator valve against spring force and torque signal fluid pressure to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the third clutch apply.

TCC apply could vary depending on vehicle application and may be calibrated to apply in Overdrive Range - Third Gear.

Release fluid pressure routed to the TFP manual valve position switch signals the PCM that the TCC is released.

Scheme 21

Overdrive Range, Fourth Gear - Torque Converter Clutch Not Applied

As the speed of the vehicle continues to increase, the powertrain control module (PCM) monitors the input signals from various engine and transmission sensors. The PCM uses this data to energize the 1-2, 3-4 shift solenoid (SS) valve in order to shift the transmission into fourth gear at the appropriate time.

1-2, 3-4 Shift Solenoid (SS) Valve (315)

Energizes to prevent fluid from exhausting out of the line passage and the 1-2, 3-4 signal fluid passage.

Is held against 1-2, 3-4 signal fluid pressure by spring pressure and 2-3 off signal fluid pressure at the end of the valve.

3-4 Shift Valve (362)

When 1-2, 3-4 signal fluid shifts the 3-4 shift valve against spring force, it allows 3rd fluid to enter the 4th clutch fluid passage. 4th clutch fluid is forced through a feed orifice before stroking the 3-4 accumulator piston (428) and applying the fourth clutch.

Fourth Clutch

4th Clutch fluid pressure applies the fourth clutch to shift the transmission to fourth gear.

Remains applied, but is ineffective.

Overruns as fourth clutch is applied. In third gear, the input clutch is released allowing input clutch apply fluid to exhaust through the 3-4 shift valve (362) into the input clutch feed passage. At the 2-3 shift valve (357), exhausting input clutch apply fluid is directed into the D3 passage and out the manual valve (404).

Remains applied.

Remains applied, but is ineffective.

Continues to overrun.

3-4 Accumulator

4th clutch fluid is also routed to the 3-4 accumulator piston. 4th clutch fluid pressure moves the piston against spring force and 3-4 accumulator feed fluid pressure. This action absorbs initial 4th clutch fluid pressure to cushion the 4th clutch apply. The movement of the 3-4 accumulator piston forces some accumulator fluid out of the accumulator.

3-4 Accumulator Valve

Excess 3-4 accumulator feed fluid is routed back to the 3-4 accumulator valve. This fluid pressure moves the accumulator valve against spring force and torque signal fluid pressure to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the fourth clutch apply.

TCC apply could vary depending on vehicle application and may be calibrated to apply in Overdrive Range - Fourth Gear.

Release fluid pressure routed to the TFP manual valve position switch signals the PCM that the TCC is released.

Scheme 22

Overdrive Range, Fourth Gear - Torque Converter Clutch Applied

The torque converter clutch applies during third or fourth gear operation after the powertrain control module (PCM) receives the appropriate input signals to energize the TCC control (PWM) solenoid. To apply the torque converter clutch, the following changes take place in the electrical and hydraulic systems

TCC Control (PWM) Solenoid

When conditions are appropriate, the PCM energizes the TCC control (PWM) solenoid to initiate the TCC apply. The solenoid is pulse width modulated (PWM) to provide a smooth TCC apply (refer to the electrical controls section for a detailed description of the TCC control (PWM) solenoid operation). When energized, the TCC control (PWM) solenoid modulates 2nd fluid into the TCC signal (PWM) fluid circuit.

TCC Regulator Valve

TCC signal (PWM) fluid pressure modulates the valve against spring force and TCC regulated apply fluid pressure. This action directs line pressure into the TCC regulated apply fluid circuit in relation to vehicle operating conditions.

TCC Control Valve

Modulated TCC signal (PWM) fluid pressure moves the valve against spring force in relation to vehicle operating conditions. This action regulates TCC regulated apply fluid into the TCC apply fluid circuit. At the same time, the TCC release fluid circuit is opened to an orificed exhaust. In this position the valve directs converter feed fluid to feed the cooler fluid circuit.

TCC apply fluid is routed to the torque converter clutch at the same time TCC release fluid exhausts from the torque converter clutch. TCC apply fluid pressure applies the TCC.

Release fluid also exhausts from the TFP manual valve position switch and the TFP manual valve position switch signals the PCM that the TCC is engaged.

Cooler Check Valve

Located in either the case cover or cooler line fitting depending on model. Allows cooler fluid to pass through the cooler and provide lubrication for the transmission. It also prevents converter drainback when the engine is off.

Number 1 Ball Check Valve (372)

Located in the case cover (400), blocks TCC release fluid while sending TCC apply fluid to the torque converter clutch blow-off valve (417-20).

Converter Clutch Blow-off Valve

Limits maximum TCC apply pressure to prevent torque converter damage.

Scheme 23

Overdrive Range, 4-3 Downshift - Torque Converter Clutch Not Applied

When the transmission is operating in Fourth gear, a 4-3 downshift will occur if there is a significant change (increase) in the throttle position or if the load on the engine is increased. When the 4-3 downshift occurs, the torque converter clutch will release prior to the shift occurring which results in the following changes in the hydraulic system

Pressure Control (PC) Solenoid

During the downshift, except for a coastdown, the PCM senses the increase in throttle position or engine load and increases the PC solenoid duty cycle. The increase in duty cycle increases output fluid pressure from the PC solenoid, thereby increasing torque signal fluid pressure at the torque signal regulator valve.

Pressure Regulator Valve

Increased torque signal fluid pressure acting on the line boost valve increases line pressure at the pressure regulator valve.

TCC Control (PWM) Solenoid Valve

As the throttle position changes, the throttle position sensor provides input to the PCM indicating throttle angle. The PCM then lowers the ON/OFF cycle time of the TCC control PWM solenoid valve, lowering TCC signal (PWM) fluid pressure.

Lowered TCC signal (PWM) fluid pressure allows the valve to move with spring pressure, allowing converter feed fluid into the TCC release circuit. TCC release fluid is then routed to the torque converter pressure plate and disengages the torque converter clutch, TCC apply fluid from the torque converter clutch pressure plate is then routed back through its circuit to the converter clutch control valve. TCC apply fluid passes through the valve and enters the cooler circuit.

When the TCC is in the release position, TCC release fluid pressure is routed to the TFP manual valve position switch. This fluid pressure signals the PCM that the TCC is in the released position.

De-energizes, allowing 1-2, 3-4 signal fluid at the 3-4 shift valve (362) to exhaust through the solenoid.

When 1-2, 3-4 signal fluid exhausts, spring force moves the valve allowing 4th clutch fluid to exhaust through the valve.

Fourth Clutch fluid is exhausted at the 3-4 shift valve and the driven support ball check valve. Fourth clutch return spring pressure moves the fourth clutch piston and releases the fourth clutch.

4th Clutch fluid exhausts from the accumulator. Spring force and 3-4 accumulator feed fluid pressure move the accumulator piston to the Third gear position.

The accumulator valve regulates line pressure into the 3-4 accumulator fluid circuit to fill the 3-4 accumulator. This regulation is basically controlled by torque signal fluid pressure. Increased torque signal fluid pressure regulates accumulator fluid to a higher pressure. Note: The clutch and band application information is the same as Overdrive Range - Third Gear.

Scheme 24

Drive Range, Manual Third (from Overdrive Range)

A manual 4-3 downshift is accomplished by moving the gear selector lever to the Manual Third (3) position. In Manual Third the transmission is hydraulically prevented from upshifting into Fourth gear under any conditions. Also, the input clutch is applied in Manual Third range to provide engine compression braking in 3rd gear. The following information explains the additional changes during a manual 4-3 downshift as compared to a forced 4-3 downshift. Refer to Overdrive Range, 4-3 Downshift - Torque Converter Clutch Not Applied for a complete description of a 4-3 downshift.

Manual Valve

The manual valve moves into the Manual Third (3) position and line pressure enters the D3 fluid circuit.

Allows D3 fluid to enter the input clutch feed passage and directs it to the 3-4 shift valve (362).

Is downshifted when D3 fluid is fed to the valve. In this position input clutch feed fluid enters the input clutch passage. 4th clutch fluid is exhausted through an orifice.

Number 3 Ball Check Valve (372)

Located in the case cover (400), it is seated against the PRN passage allowing input clutch fluid to apply the input clutch.

When de-energized, it allows 1-2, 3-4 signal fluid from the 3-4 shift valve (362) to exhaust through the solenoid. However, this event does not have to occur in order to achieve a manual 4-3 downshift.

Manual Third-Second and First Gears

The transmission operates the same in Manual Third as in Overdrive range with the exception of Fourth gear being prevented. The transmission will upshift and downshift between First, Second and Third gears as in Overdrive range. However, engine compression braking is not available in Manual Third - First gear and the vehicle will coast when the throttle is released.

Scheme 25

Drive Range, Manual Second (from Drive, Manual Third)

When the gear selector lever is moved to the Manual Second (D2) gear range, the manual valve moves and allows line pressure to enter the D2 fluid passage. The transmission reacts by shifting immediately into second gear range and is prevented from upshifting into either Third or Fourth gear.

Is moved by the gear selector lever allowing line pressure to enter the D2 passage.

Number 8 Ball Check Valve (372)

Located in the control valve body (300), is fed D2 fluid from the manual valve (404) and directs it to the 2-3 shift valve (357).

When shifted by D2 fluid, it allows D2 to enter the manual 2-1 servo feed passage to stroke the manual 2-1 servo assembly (104-115) and allows 3rd fluid to exhaust.

Manual 2-1 Servo Assembly (104-115)

Applies the manual 2-1 band (680) during manual second and manual first gear ranges.

Located in the case cover (400), it directs 3rd clutch/lo-1st exhaust fluid into the 3rd clutch passage, releasing the 3rd clutch.

When energized, it allows line pressure to enter the 2-3 signal fluid passage and sends it to the 4-3 manual downshift valve (360) and 3-2 manual downshift valve (356). However, this event does not have to occur in order to achieve a manual 3-2 downshift.

3-2 Manual Downshift Valve (356)

Is shifted by 2-3 signal fluid and prevents the 2-3 shift valve (357) from upshifting.

The PCM increases the PC solenoid duty cycle to increase the operating range of torque signal fluid pressure in Manual Second. This provides increased line pressure for the additional torque requirements during engine compression braking and increased engine load in Manual Second.

The PCM will release the TCC before downshifting into Manual Second. The TCC will not re-apply in Second gear under normal operating conditions.

Scheme 26

Drive Range, Manual First (from Drive, Manual Second)

A manual 2-1 downshift is initiated by moving the gear selector lever to the Manual First (1) position. However, the transmission will not downshift into First gear until vehicle speed is below approximately 60 km/h (37 mph). At higher vehicle speeds the PCM will keep 1-2 shift solenoid (SS) valve de-energized (OFF) and the transmission will operate in Manual First - Second Gear. In Manual First the transmission is electronically prevented from upshifting into Third or Fourth gears under any conditions. Also, the third clutch is applied in Manual First - First Gear to provide engine compression braking.

Line pressure is routed into the Lo fluid circuit when the selector lever is moved into the Manual First (1) position. Line pressure continues to feed the D4, D3 and D2 fluid circuits as in Manual Second.

Number 7 Ball Check Valve (372)

Located in the control valve body (300), directs Lo fluid to the 1-2 shift valve (318).

When shifted against spring force, allows Lo fluid to enter the Lo-1st passage to the pressure regulator valve (313). During release of the 2nd clutch, exhausting 2nd fluid passes through the valve and enters the 3rd fluid passage.

Lo Blow Off Valve (407)

A relief valve that exhausts excess Lo fluid pressures above 448 kPa (65 psi) from the 3rd clutch apply circuit.

Located in the case cover (400), it seats against 3rd clutch fluid allowing Lo-1st fluid to enter the 3rd clutch fluid passage and apply the 3rd clutch.

Energizes, allowing line pressure to feed into the 1-2, 3-4 signal fluid passage and to the 3-4 shift valve (362).

Located in the case cover (400), forces exhausting 2nd clutch apply fluid through an orifice into the 2nd clutch passage and to the 1-2 shift valve (318).

Lo fluid is directed through the 1-2 shift valve (318) into the Lo-1st fluid passage. Lo-1st fluid is sent to the pressure regulator valve (313) to boost line pressure and at the same time to the Lo blow off valve (407). The addition of Lo-1st fluid pressure increases the operating range of line pressure in Manual First.

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See also:
• Electronic Component Description
• Overdrive Range, 4-3 Downshift - Torque Converter Clutch Not Applied