Automatic Transmission - 4l60-e (m30) - Description and Operation Chevrolet Express G2500

How to Use This Section

This section 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 manual. 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 1

Scheme 2

Scheme 3

Plant and Shift Build Chart

Transmission Component and System Description

The mechanical components of the 4L60-E 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 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. Torque converter assembly
3. Servo assembly and 2-4 band assembly
4. Reverse input clutch and housing
5. Overrun clutch
6. Forward clutch
7. 3-4 clutch
8. Forward sprag clutch assembly
9. Lo and reverse roller clutch assembly
10. Lo and reverse clutch assembly
11. Two planetary gear sets: Input and Reaction
12. Oil pump assembly
13. Control valve body assembly

The electrical components of the 4L60-E are as follows

1. 1-2 and 2-3 shift solenoid valves
2. Transmission pressure control (PC) solenoid
3. Torque converter clutch (TCC) solenoid valve
4. TCC pulse width modulation (PWM) solenoid valve
5. Automatic transmission fluid temperature (TFT) sensor
6. Vehicle speed sensor assembly

For more information, refer to Electronic Component Description .

Transmission Adaptive Functions

The 4L60-E transmission utilizes a line pressure control system during upshifts to compensate for the normal wear of transmission components. By adjusting the line pressure, the powertrain control module (PCM)/transmission control module (TCM) can maintain acceptable transmission shift times. This process is known as "adaptive learning" or "shift adapts" and is similar to the closed loop fuel control system used for the engine.

In order for the PCM/TCM to perform a "shift adapt," it must first identify if an upshift is acceptable to analyze. For example, upshifts that occur during cycling of the A/C compressor or under extreme throttle changes could cause the PCM/TCM to incorrectly adjust line pressure. When an upshift is initiated, a number of contingencies, such as throttle position, transmission temperature, and vehicle speed, are checked in order to determine if the actual shift time is valid to compare to a calibrated desired shift time. If all the contingencies are met during the entire shift, then the shift is considered valid and the adapt function may be utilized if necessary.

Once an adaptable shift is identified, the PCM/TCM compares the actual shift time to the desired shift time and calculates the difference between them. This difference is known as the shift error. The actual shift time is determined from the time that the PCM/TCM commands the shift to the start of the engine RPM drop initiated by the shift. If the actual shift time is longer than the calibrated desired shift time, a soft feel or slow engagement, then the PCM/TCM decreases current to the pressure control (PC) solenoid in order to increase line pressure for the next, same, upshift under identical conditions. If the actual shift time is shorter than the calibrated desired shift time, a firm engagement, then the PCM/TCM increases current to the PC solenoid in order to decrease line pressure for the next, same, upshift under identical conditions.

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

Clearing Transmission Adaptive Pressure (TAP)

Transmission adaptive pressure (TAP) information is displayed and may be reset using a scan tool.

The adapt function is a feature of the PCM/TCM that either adds or subtracts line pressure from a calibrated base line pressure in order to compensate for normal transmission wear. 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/TCM has adjusted line pressure at or below the calibrated base line pressure.

Updating TAP information is a learning function of the PCM/TCM 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/TCM will need to relearn TAP values. Transmission performance may be affected as new TAPs are learned. Learning can only take place when the PCM/TCM has determined that an acceptable shift has occurred. The PCM/TCM must also relearn TAP values if it is replaced.

Scheme 4

The 1-2 and 2-3 shift solenoid valves (also called A and B solenoids) are identical devices that control the movement of the 1-2 and 2-3 shift valves. The 3-4 shift valve is not directly controlled by a shift solenoid. The solenoids are normally-open exhaust valves that work in 4 combinations to shift the transmission into different gears.

The powertrain control module (PCM) or transmission control module (TCM) energizes each solenoid by grounding the solenoid through an internal quad driver. This sends current through the coil winding in the solenoid and moves the internal plunger out of the exhaust position. When ON, the solenoid redirects fluid to move a shift valve.

The PCM/TCM-controlled shift solenoids eliminate the need for TV and governor pressures to control shift valve operation.

Scheme 5

The transmission pressure control solenoid is an electronic pressure regulator that controls pressure based on the current flow through its coil winding. The magnetic field produced by the coil moves the solenoid's internal valve which varies pressure to the pressure regulator valve.

The powertrain control module (PCM) or transmission control module (TCM) controls the pressure control solenoid by commanding current between 0.1-1.1 amps. This changes the duty cycle of the solenoid, which can range between 5-95 percent, typically less than 60 percent. High amperage (1.1 amps) corresponds to minimum line pressure, and low amperage (0.1 amp) corresponds to maximum line pressure, if the solenoid loses power, the transmission defaults to maximum line pressure.

The PCM/TCM commands the line pressure values, using inputs such as engine speed and throttle position sensor voltage.

The pressure control solenoid takes the place of the throttle valve or the vacuum modulator that was used on past model transmissions.

Scheme 6

The torque converter clutch (TCC) solenoid valve is a normally-open exhaust valve that is used to control torque converter clutch apply and release. When grounded, energized, by the powertrain control module (PCM) or transmission control module (TCM), the TCC solenoid valve stops converter signal oil from exhausting. This causes converter signal oil pressure to increase and move the TCC solenoid valve into the apply position.

Scheme 7

The torque converter clutch pulse width modulation solenoid valve controls the fluid acting on the converter clutch valve. The converter clutch valve controls the torque converter clutch (TCC) apply and release. This solenoid is attached to the control valve body assembly within the transmission. The TCC PWM solenoid valve provides a smooth engagement of the torque converter clutch by operating during a duty cycle percent of ON time.

Scheme 8

The vehicle speed sensor (VSS) provides vehicle speed information to the powertrain control module (PCM) or transmission control module (TCM). The VSS is a permanent magnet (PM) generator. The PM generator produces a pulsing AC voltage as rotor teeth on the transmission output shaft pass through the sensor's magnetic field. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. Output voltage varies with speed from a minimum of 0.5 volts at 100 RPM to more than 100 volts at 8,000 RPM. The PCM/TCM converts the pulsing voltage to vehicle speed. The PCM/TCM uses the vehicle speed signal to determine shift timing and TCC scheduling.

Automatic Transmission Fluid Temperature Sensor

The automatic transmission fluid temperature (TFT) sensor is part of the automatic transmission manual shift shaft position switch. The TFT sensor is a resistor, or thermistor, which changes value based on temperature. The sensor has a negative-temperature coefficient. This means that as the temperature increases, the resistance decreases and as the temperature decreases, the resistance increases.

The powertrain control module (PCM) or transmission control module (TCM) supplies a 5-volt reference signal to the TFT sensor and measures the voltage drop in the circuit. When the transmission fluid is cold, the sensor resistance is high and the PCM/TCM detects high signal voltage. As the fluid temperature warms to a normal operating temperature, the resistance becomes less and the signal voltage decreases. Refer to Transmission Fluid Temperature Sensor Specifications for a complete comparison of sensor resistance, temperature and signal voltage.

The PCM/TCM uses the TFT sensor information to control shift quality and TCC application.

Scheme 9

The internal mode switch (IMS)/transmission range (TR) switch is part of the park/neutral position (PNP) and backup lamp switch assembly, which is internally mounted on the transmission manual shaft. The IMS/TR switch contains four internal switches that indicate the transmission gear range selector lever position. The transmission control module (TCM) or powertrain control module (PCM) supplies ignition voltage to each switch circuit. As the gear range selector lever is moved, the state of each switch may change, causing the circuit to open or close. An open circuit or switch indicates a high voltage signal. A closed circuit or switch indicates a low voltage signal. The TCM/PCM detects the selected gear range by deciphering the combination of the voltage signals. The TCM/PCM compares the actual voltage combination of the switch signals to a IMS/TR switch combination chart stored in memory.

The PNP switch contains one internal switch that indicates the transmission gear range selector lever position when in Park and Neutral. The engine control module (ECM)/PCM supplies ignition voltage to the PNP switch circuit. As the gear range selector lever is moved, the state of the PNP switch changes, causing the circuit to open or close. An open circuit or switch indicates a high voltage signal. A closed circuit or switch indicates a low voltage signal. The ECM/PCM detects the Park and Neutral ranges by voltage signal.

Scheme 10

Tow/Haul mode enables the operator to achieve enhanced shift performance when towing or hauling a load. When tow/haul mode is selected, the tow/haul switch input signal to the body control module (BCM) is momentarily toggled to zero volts. This signals the powertrain control module (PCM) or transmission control module (TCM) to extend the length of time between upshifts and increase transmission line pressure. Cycling the tow/haul switch again disables tow/haul mode and returns the transmission to a normal shift pattern.

Scheme 11

The transmission manual shift shaft switch assembly (88) is a sliding contact switch attached to the manual shift shaft inside the transmission case. The five inputs to the TCM from the transmission manual shift shaft switch assembly indicate the transmission gear selector lever position. This information is used for engine controls as well as determining the transmission shift patterns. The state of each input is available for display on the scan tool. The five input parameters represented are Signal A, Signal B, Signal C, Signal P (Parity) and Signal N (P/N Start).

Park - Engine Running

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

Pressure Regulator Valve

The pressure regulator valve regulates the oil pump output (line pressure) in response to the signal fluid pressure, the spring force and the line pressure acting on the end of the valve. The line pressure is routed through the valve and into both the converter feed and the decrease fluid circuits. Regulated line pressure is also directed to the manual valve, the converter clutch valve, the actuator feed limit valve, and the regulated apply valve.

Pressure Relief Valve

Controlled by spring force, this checkball limits the maximum value of the line pressure. When the line pressure reaches this limiting value, fluid is exhausted past the ball and returns to the sump.

Line Pressure Tap

The line pressure tap provides a location to measure the line pressure with a fluid pressure gauge.

Actuator Feed Limit Valve

Biased by spring force and orificed AFL fluid, it limits the maximum value of line pressure entering the AFL fluid circuit. Below this limiting value, the AFL fluid pressure equals the line pressure. The AFL fluid is routed to the pressure control solenoid valve, the TCC PWM solenoid valve, the 1-2 and 2-3 shift solenoid valves, and the 2-3 shift valve train.

Pressure Control (PC) Solenoid Valve

Controlled by the powertrain control module (PCM), the PC solenoid valve regulates the filtered AFL fluid into the torque signal fluid pressure. The PCM controls this regulation by varying the current value to the PC solenoid valve in relation to the throttle position and other vehicle operating conditions.

Torque Converter Clutch (TCC)

Torque Converter Clutch PWM Solenoid and Regulator Apply and Isolator Valve

AFL fluid is routed to the TCC PWM solenoid valve, in Park the PCM has the duty cycle turned OFF. This prevents AFL fluid from entering the converter clutch signal fluid circuit. Regulated line pressure is routed to the regulator apply valve, which is open with CC signal circuit empty, and blocks line pressure from entering the regulated apply circuit. Any fluid in the regulated apply circuit will exhaust at the regulated apply valve.

TCC Solenoid Valve

Under normal operating conditions, the PCM keeps the normally open TCC solenoid valve de-energized (OFF). Converter feed fluid exhausts through the open TCC solenoid valve, and spring force keeps the converter clutch apply valve in the release position.

Converter Clutch Valve

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

Torque Converter

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

Cooler and Lubrication System

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

Manual Valve

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

Lo and Reverse Clutch Applies

Lo and Reverse Clutch Piston

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

Lo Overrun Valve

The PR fluid pressure moves the valve against the spring force and fills the Lo/reverse fluid circuit. Lo/reverse fluid is orificed (323) back to the lo overrun valve in order to assist the PR fluid in moving the valve against the spring force. The spring force provides a time delay for the PR fluid filling the Lo/reverse fluid circuit. The Lo/reverse fluid is routed to the inner area of the lo and reverse clutch piston in order to increase the holding capacity of the clutch.

Shift Solenoid Valves (1-2 and 2-3)

Both shift solenoid valves, which are normally open, are energized by the PCM and block fluid from exhausting. This maintains the signal A fluid pressure at the 1-2 shift solenoid valve and signal B fluid pressure at the 2-3 shift solenoid valve.

Shift Valves (1-2, 2-3 and 3-4)

Signal A fluid pressure holds the 1-2 shift valve in the downshift position and the 3-4 valve in the upshift (first and fourth gear) position. The signal B fluid pressure from the 2-3 shift solenoid valve holds the 2-3 shift valve train in the downshift position.

Scheme 12

Reverse

When the gear selector lever is moved to the Reverse (R) position (from the Park position), the following changes occur to the transmissions hydraulic and electrical systems

The manual valve moves to the Reverse position and line pressure enters the reverse fluid circuit. As in Park, line pressure also fills the PR (Park/Reverse) fluid circuit. All other fluid circuits are blocked by the manual valve.

Lo and Reverse Clutch

As in Park, PR fluid pressure acts on the outer area of the lo and reverse clutch piston to apply the lo and reverse clutch. Also, Lo/reverse fluid from the lo overrun valve acts on the inner area of the piston to increase the holding capacity of the clutch.

Reverse Input Checkball (#3)

Reverse fluid pressure seats the #3 checkball, flows through orifice #17 and fills the reverse input fluid circuit. This orifice helps control the reverse input clutch apply rate when engine speed is at idle.

Reverse Abuse Valve

Reverse fluid pressure acts on the end of the valve opposite of spring force. At engine speeds above idle, reverse fluid pressure, which is fed by line pressure, increases and moves the valve against spring force (as shown). Reverse fluid can then fill the reverse input fluid circuit through the reverse abuse valve. This bypasses the control of orifice #17 and provides a faster clutch apply.

Boost Valve

Reverse input fluid pressure moves the boost valve against the pressure regulator valve spring. The spring acts on the pressure regulator valve to increase the operating range of line pressure in Reverse. Reverse input fluid also flows through the valve and to the reverse input clutch piston. Remember that torque signal fluid pressure continually acts on the boost valve to control line pressure in response to vehicle operating conditions.

Reverse Input Clutch Piston

Reverse input fluid pressure moves the piston to apply the reverse input clutch plates and obtain Reverse.

Reverse Input Air Bleed Checkball

This ball and capsule is located in the reverse input fluid circuit in the oil pump to provide an air escape when the fluid pressure increases. It also allows air into the circuit to displace the fluid when the clutch releases.

Both shift solenoid valves are energized as in the Park range. Signal A and signal B fluids are blocked from exhausting through the shift solenoid valves to maintain fluid pressure in these circuits at the end of the shift valves.

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

The PC solenoid valve continues to regulate AFL fluid into torque signal fluid pressure. The PCM varies the current at the solenoid to regulate torque signal fluid pressure in response to throttle position and other PCM input signals. Torque signal fluid pressure is used to control line pressure at the boost and pressure regulator valves.

Scheme 13

Neutral - Engine Running

When the gear selector lever is moved to the Neutral position (N) from the Reverse position, the following changes occur to the transmission hydraulic and electrical systems.

In the Neutral position, the manual valve blocks the line pressure from entering any other fluid circuits. Reverse and PR fluids exhaust past the manual valve.

Lo and Reverse Clutch Releases

Lo and Reverse Clutch Piston

PR and Lo/reverse fluids exhaust from the piston, thereby releasing the lo and reverse clutch plates. Exhausting PR fluid unseats the lo and reverse clutch checkball (#10) for a quick exhaust.

Spring force closes the valve when the PR fluid pressure exhausts. Lo/reverse fluid exhausts through the valve, into the Lo/1st fluid circuit, past the 1-2 shift valve, into the Lo fluid circuit and through an exhaust port at the manual valve.

Reverse Input Cutch Releases

Reverse Input Clutch Piston

Reverse input fluid pressure exhausts from the piston, through the boost valve, past the #3 checkball and to the manual valve. With the reverse input fluid exhausted, the reverse input clutch plates are released and the transmission is in Neutral.

Reverse fluid pressure exhausts and spring force closes the valve.

Reverse input fluid pressure exhausts and line pressure returns to the normal operating range as in the Park and Overdrive positions.

Exhausting reverse input fluid unseats the ball for a quick exhaust through the reverse fluid circuit and past the manual valve.

Scheme 14

Overdrive Range, First Gear

When the gear selector lever is moved to the Overdrive position, from the neutral position, the following changes occur to the transmission's hydraulic and electrical systems

Line pressure flows through the manual valve and fills the D4 fluid circuit. All other fluid circuits remain empty with the manual valve in the Overdrive position.

Forward Clutch Accumulator Checkball (#12)

D4 fluid pressure seats the checkball and is orificed (#22) into the forward clutch feed fluid circuit. This orifice helps control the forward clutch apply rate.

Forward Clutch Accumulator Piston

Forward clutch feed fluid pressure moves the piston against spring force. This action absorbs some of the initial increase of forward clutch feed fluid pressure to cushion the forward clutch apply.

Forward Clutch Abuse Valve

D4 fluid pressure acts on the valve opposite of spring force. At engine speeds greater than idle, D4 fluid pressure increases and moves the valve against spring force (as shown). D4 fluid can then quickly fill the forward clutch feed fluid circuit, thereby bypassing the control of orifice #22 and providing a faster apply of the forward clutch. Otherwise, with increased throttle opening and engine torque, the clutch may slip during apply.

1-2 Shift Solenoid (SS) Valve

Energized (ON) as in Neutral, the normally open solenoid is closed and blocks signal A fluid from exhausting through the solenoid. This maintains pressure in the signal A fluid circuit.

2-3 Shift Solenoid (SS) Valve

Energized (ON) as in Neutral, the normally open solenoid is closed and blocks signal B fluid from exhausting through the solenoid. This maintains signal B fluid pressure at the solenoid end of the 2-3 shift valve.

2-3 Shift Valve Train

Signal B fluid pressure at the solenoid end of the 2-3 shift valve holds the valve train in the downshifted position against AFL fluid pressure acting on the 2-3 shift valve. In this position, the 2-3 shuttle valve blocks AFL fluid from entering the D432 fluid circuit. The D432 fluid circuit is open to an exhaust port past the valve.

1-2 Shift Valve

Signal A fluid pressure holds the valve in the downshifted position against spring force. In the First gear position, the valve blocks D4 fluid from entering the 2nd fluid circuit.

Accumulator Valve

Biased by torque signal fluid pressure, spring force and orificed accumulator fluid pressure at the end of the valve, the accumulator valve regulates D4 fluid into accumulator fluid pressure. Accumulator fluid is routed to both the 1-2 and 3-4 accumulator assemblies in preparation for the 1-2 and 3-4 upshifts respectively.

Rear Lube (Model Dependent)

D4 fluid is routed through an orifice cup plug (#24) in the rear of the transmission case to feed the rear lube fluid circuit.

Remember that the PC solenoid valve continually varies torque signal fluid pressure in relation to throttle position and vehicle operating conditions. This provides a precise control of line pressure.

Torque Converter Clutch PWM Solenoid Valve

In first gear, at approximately 6 mph, the PCM operates the TCC PWM solenoid valve at approximately a 90 percent duty cycle. This opens the AFL fluid circuit, to fill the converter clutch signal fluid circuit through the #9 orifice, and flows to the isolator valve. The CC signal fluid pressure, acting on the isolator valve, will move the regulated apply valve towards the closed position. Regulated line pressure is now routed into the regulated apply circuit, and flows to the closed converter clutch valve, and is blocked from entering the converter clutch apply circuit. Regulated apply fluid is routed through the #8 orifice to the front of the regulated apply valve, and regulates the line pressure entering the regulated apply circuit, in response to the CC signal fluid acting on the isolator valve.

Scheme 15

Overdrive Range, Second Gear

As vehicle speed increases and other operating conditions are appropriate, the PCM de-energizes the 1-2 shift solenoid valve in order to shift the transmission to second gear.

De-energized (turned OFF) by the PCM, the normally open solenoid opens and signal A fluid exhausts through the solenoid.

Energized (ON) as in first gear, the 2-3 shift solenoid valve blocks signal B fluid from exhausting through the solenoid. This maintains signal B fluid pressure at the solenoid end of the 2-3 shift valve.

Without signal A fluid pressure, spring force moves the valve into the upshift position. D4 fluid is routed through the valve and fills the 2nd fluid circuit.

1-2 Shift Checkball (#8)

The 2nd fluid pressure seats the #8 checkball, flows through orifice #16, and fills the 2nd clutch fluid circuit. This orifice helps control the 2-4 band apply rate.

2-4 Servo Assembly

The 2nd clutch fluid pressure moves the #8 checkball, flows through orifice #16 and fills the 2nd clutch fluid circuit. This orifice helps to control the 2-4 band apply rate.

1-2 Accumulator

The 2nd clutch fluid pressure also moves the 1-2 accumulator piston against the spring force and the accumulator fluid pressure. This action absorbs the initial 2nd clutch fluid pressure in order to cushion the 2-4 band apply rate. Also, the movement of the 1-2 accumulator piston forces some accumulator fluid out of the accumulator assembly. This accumulator fluid is routed back to the accumulator valve.

The accumulator fluid forced out of the 1-2 accumulator is orificed (#30) to the end of the accumulator valve. This pressure moves the valve against the spring force and the torque signal fluid pressure in order to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the 2-4 band apply rate. The fluid circuit shows the exhaust of the accumulator fluid during the shift by the arrow directions in the accumulator fluid circuit.

The signal B fluid pressure from the 2-3 shift solenoid valve holds the valve train in the downshift position. The 2nd fluid is routed through the 2-3 shuttle valve and fills the servo feed fluid circuit.

3-4 Relay Valve and 4-3 Sequence Valve

Spring force holds these valves in the downshift position (first, second and third gear positions). The 2nd fluid is blocked by the 3-4 relay valve and the servo feed fluid is blocked by both valves in preparation for a 3-4 upshift.

3-2 Downshift Valve

Spring force holds the valve closed, blocking the 2nd fluid and the 2nd clutch fluid. This valve is used in order to help control the 3-2 downshift.

3-4 Shift Valve

Signal A fluid pressure exhausts and spring force moves the valve into the downshift position (second and third gear positions).

Torque Converter Clutch

TCC Solenoid Valve

Under normal operating conditions, in Overdrive Range-Second Gear, the PCM keeps the normally open TCC solenoid valve de-energized. Converter feed fluid exhausts through the open solenoid, and spring force keeps the converter clutch apply valve in the release position.

Scheme 16

Overdrive Range, Third Gear

As vehicle speed increases further and other vehicle operating conditions are appropriate, the PCM de-energizes the normally open 2-3 shift solenoid valve in order to shift the transmission into Third gear.

Note. AFL fluid continues to feed signal B fluid to the solenoid through orifice #29. However, the exhaust port through the solenoid is larger than orifice #29 to prevent a buildup of pressure in the signal B fluid circuit at the solenoid end of the 2-3 shift valve. Exhausting signal B fluid is represented by the arrows through the solenoid.

De-energized (turned OFF) by the PCM, the solenoid opens and actuator feed limit signal B fluid exhausts through the solenoid.

AFL fluid pressure at the 2-3 shift valve moves the valve train toward the solenoid. In the upshifted position, the following changes occur

1. AFL fluid is routed through the 2-3 shift valve and fills the D432 fluid circuit.
2. 2nd fluid is blocked from entering the servo feed fluid circuit and is orificed (#28) into the 3-4 signal fluid circuit. This orifice helps control the 3-4 clutch apply rate.
3. Servo feed fluid exhausts past the valve into the 3-4 accumulator fluid circuit and through an exhaust port at the 3-4 relay valve.

3-4 Clutch Exhaust Checkball (#4)

3-4 signal fluid unseats the ball and enters the 3-4 clutch fluid circuit.

3-4 Clutch Piston

3-4 clutch fluid pressure moves the piston to apply the 3-4 clutch plates and obtain 3rd gear. However, the 2-4 band must release as the 3-4 clutch applies.

3rd Accumulator Checkball (#2)

3-4 clutch fluid pressure unseats the ball and fills the 3rd accumulator fluid circuit.

3rd Accumulator Exhaust Checkball (#7)

3rd accumulator fluid seats the ball against the orificed exhaust and is routed to the released side of the 2nd apply piston. Before the #7 checkball seats, air in the 3rd accumulator fluid circuit is exhausted through the orifice.

3rd accumulator fluid pressure acts on the release side of the 2nd apply piston and assists servo return spring force. The surface area on the release side of the piston is greater than the surface area on the apply side. Therefore, 3rd accumulator fluid pressure and servo return spring force move the 2nd apply piston against 2nd clutch fluid pressure. This action serves two functions

1. Move the apply pin to release the 2-4 band.
2. Act as an accumulator by absorbing initial 3-4 clutch fluid to cushion the 3-4 clutch apply rate. Remember that the 3rd accumulator fluid circuit is fed by 3-4 clutch fluid.

3-4 clutch fluid pressure moves the valve against spring force. This opens the valve and allows 2nd fluid to feed the 2nd clutch fluid circuit through the valve.

1-2 Shift Solenoid (SS) Valve and 1-2 Shift Valve

The 1-2 SS valve remains de-energized and signal A fluid is exhausted through the solenoid. Also, D432 fluid pressure from the 2-3 shift valve assists spring force to hold the 1-2 shift valve in the upshifted position.

Spring force holds the valve in the downshifted position, blocking 3-4 clutch fluid in preparation for a 3-4 upshift.

TCC Solenoid Valve

Under normal operating conditions, in Overdrive Range-Third Gear, the PCM keeps the normally open TCC solenoid valve de-energized. Converter feed fluid exhausts through the open solenoid, and spring force keeps the converter clutch apply valve in the release position. However, at speeds above approximately 121 km/h (75 mph), with the transmission still in third gear, the PCM will command TCC apply in third gear. Refer to Overdrive Range, Fourth Gear - Torque Converter Clutch Applied for more information on TCC apply.

Scheme 17

Overdrive Range, Fourth Gear - Torque Converter Clutch Applied

At higher vehicle speeds, the Hydra-matic 4L60-E transmission uses an overdrive gear ratio (fourth gear) in order to increase fuel economy and in order to maximize engine performance. When vehicle operating conditions are appropriate, the PCM energizes the 1-2 shift solenoid valve to shift the transmission into fourth gear.

Energized (turned ON) by the PCM, the normally open solenoid closes and blocks signal A fluid from exhausting through the solenoid. This creates pressure in the signal A fluid circuit.

De-energized (OFF) as in third gear, the 2-3 shift solenoid valve exhausts signal B fluid through the solenoid.

D432 fluid pressure from the 2-3 shift valve and spring force hold the valve in the upshift position against signal A fluid pressure.

Signal A fluid pressure moves the valve into the upshift position against the spring force. In this position, the valve routes 3-4 signal fluid into the 4th signal fluid circuit.

4th signal fluid pressure moves both valves into the upshift (fourth gear) position against the spring force acting on the 4-3 sequence valve. This causes the following changes

1. Orificed (#7) 2nd fluid is routed through the 3-4 relay valve and into the servo feed fluid circuit.
2. Servo feed fluid is routed through the 4-3 sequence valve and into the 4th fluid circuit.
3. 3-4 accumulator fluid routed from the 2-3 shuttle valve is blocked by both valves.

4th fluid is routed through the center of the servo apply pin and acts on the apply side of the 4th apply piston. 4th fluid pressure moves the 4th apply piston against the apply pin spring force acting on the release side of the 4th apply piston. This action moves the apply pin and applies the 2-4 band in order to obtain fourth gear.

2-4 Band Apply Accumulation

2-3 Shift Valve Train

The valve train remains in the upshift position with the AFL fluid pressure acting on the 2-3 shift valve. In addition to its operation third gear, the 2-3 shift valve directs servo feed fluid into the 3-4 accumulator fluid circuit.

3-4 Accumulator Assembly

3-4 accumulator fluid pressure moves the 3-4 accumulator piston against spring force and orificed accumulator fluid pressure. This action absorbs initial 4th clutch apply fluid pressure in order to cushion the 2-4 band apply. Remember that both of the 3-4 accumulator and 4th fluid circuits are fed by servo feed fluid. As 3-4 accumulator fluid fills the accumulator, any air in the system will exhaust through office #19. This piston movement forces some orificed accumulator fluid out of the 3-4 accumulator assembly.

3-4 Accumulator Checkball (#1)

The accumulator fluid forced from the accumulator unseats the #1 checkball and enters the accumulator fluid circuit. This fluid is routed to the accumulator valve. This is shown by the arrow directions in the fluid circuit.

Accumulator fluid forced from the 3-4 accumulator is orificed to the end of the accumulator valve. This fluid pressure, in addition to spring force and torque signal fluid pressure, regulates the exhaust of excess accumulator fluid pressure through the middle of the valve. This regulation helps control the 2-4 band apply feel.

Torque Converter Clutch Applies

TCC Solenoid Valve

When operating conditions are appropriate, the PCM energizes the normally open TCC solenoid valve. This closes the solenoid, blocks the converter feed fluid from exhausting, and creates pressure in the converter feed fluid circuit at the converter clutch apply valve and TCC solenoid valve.

Converter Clutch Apply Valve

Converter feed fluid pressure moves the valve against spring force and into the apply position. In this position, release fluid is open to an exhaust port, and regulated apply fluid fills the apply fluid circuit. Converter feed fluid is routed through the converter clutch apply valve to feed the cooler fluid circuit.

Release fluid from behind the pressure plate exhausts through the end of the turbine shaft. Apply fluid pressure is routed between the converter hub and stator shaft where it enters the torque converter. This fluid applies the converter clutch against the converter cover and keeps the converter filled with fluid.

TCC Apply Checkball (#9)

Release fluid, exhausting from the converter, seats the #9 checkball located in the end of the turbine shaft, and is orificed around the ball. Orificing the exhausting release fluid controls the converter clutch apply rate, along with the TCC PWM solenoid valve.

TCC PWM Solenoid Valve

The torque converter clutch pulse width modulation (TCC PWM) solenoid valve controls the regulated apply valve position. This is done through the use of pulse width modulation (duty cycle operation). The solenoid duty cycle is controlled by the PCM in relation to vehicle operating conditions and regulates actuator feed limit (AFL) fluid into the CC signal circuit, through the #9 orifice, and to the isolator valve. This controls line pressure flow through the regulated apply valve, into the regulated apply circuit, and provides a smooth engagement of the TCC.

Scheme 18

Overdrive Range, 4-3 Downshift

When the transmission is operating in fourth gear, a forced 4-3 downshift occurs if there is a significant increase in throttle position. At minimum throttle, the vehicle speed decreases gradually (coastdown) and the PCM commands a 4-3 downshift. The PCM also initiates a forced 4-3 downshift when the throttle position remains constant but engine load is increased, such as driving up a steep incline. To achieve a 4-3 downshift, the PCM de-energizes the 1-2 shift solenoid valve and the following changes occur to the transmission's electrical and hydraulic systems

De-energized by the PCM, the normally open solenoid opens and signal A fluid exhausts through the solenoid.

As in Fourth gear, D432 fluid pressure and spring force hold the valve in the upshift position.

2-4 Band Releases

3-4 Shift Valve

With the signal A fluid pressure exhausted, the spring force moves the valve into the downshift position. In this position, the valve blocks the 3-4 signal fluid and the 4th signal fluid exhausts past the valve.

These valves control the timing of the 2-4 band release. With the 4th signal fluid pressure exhausted, the 3-4 accumulator fluid pressure moves the 3-4 relay valve into the third gear position. This opens the 3-4 accumulator fluid to an orificed exhaust (#5) past the 3-4 relay valve (shown by red arrows). Because the exhaust is orificed, the 3-4 accumulator fluid pressure momentarily holds the 4-3 sequence valve against spring force before completely exhausting.

When the exhausting 3-4 accumulator fluid pressure decreases sufficiently, the spring force moves the 4-3 sequence valve into the third gear position as shown. This opens both the 3-4 accumulator and the 4th fluid circuits to a quick exhaust past the 4-3 sequence valve. In this position the valve blocks the 2nd fluid from entering the servo feed fluid circuit.

The 4th fluid exhausts from the 4th apply piston in the servo assembly. The apply pin spring moves the 4th apply piston and the apply pin in order to release the band from the reverse input drum and shift the transmission into third gear.

The 3-4 accumulator fluid exhausts from the 3-4 accumulator piston. The orificed accumulator fluid pressure and the spring force move the piston into a third gear position.

As the accumulator fluid fills the 3-4 accumulator, it seats the #1 checkball and is forced through orifice #18. This orifice controls the rate at which accumulator fluid pressure fills the 3-4 accumulator and the 3-4 accumulator fluid exhausts from the accumulator assembly.

Biased by torque signal fluid pressure and spring force, the accumulator valve regulates the D-4 fluid into the accumulator fluid circuit.

This solenoid remains de-energized as in fourth gear and the signal B fluid exhausts through the solenoid.

The AFL fluid pressure at the 2-3 shift valve holds the valves in the upshift position. This allows the servo feed fluid to exhaust through the valve, into the 3-4 accumulator fluid circuit and past the 4-3 sequence valve.

Torque Converter Clutch Solenoid Valve

TCC PWM Solenoid Valve

The PCM de-energizes the TCC solenoid valve, and operates the duty cycle of the TCC PWM solenoid valve to release the converter clutch for a smooth disengagement, prior to initiating the 4-3 downshift.

Remember that the PC solenoid valve continually adjusts the torque signal fluid pressure in relation to the various PCM input signals (mainly the throttle position).

Scheme 19

Overdrive Range, 3-2 Downshift

Similar to a forced 4-3 downshift, a forced 3-2 downshift can occur because of minimum throttle (coastdown conditions), heavy throttle or increased engine load. In order to achieve a forced 3-2 downshift, the PCM energizes the 2-3 shift solenoid valve and the following changes occur

Energized by the PCM, the normally open solenoid closes and blocks the signal B fluid from exhausting through the solenoid. This creates pressure in the signal B fluid circuit at the solenoid end of the 2-3 shift valve.

The signal B fluid pressure from the shift solenoid moves both valves to the downshift position against AFL fluid pressure acting on the 2-3 shift valve. This causes the following changes

1. The AFL fluid is blocked from the D432 fluid circuit and the D432 fluid exhausts past the 2-3 shuttle valve.
2. The 2nd fluid is blocked from feeding the 3-4 signal fluid circuit and the 2nd fluid is routed into the servo feed fluid circuit.
3. The 3-4 signal fluid is exhausted past the valve. The 3-4 clutch fluid and the 3rd accumulator fluid, which were fed by the 3-4 signal fluid, also exhaust.

3-4 Clutch Releases and 2-4 Band Applies

3-4 Clutch Piston

The 3-4 clutch fluid exhausts from the piston and the 3-4 clutch plates are released.

Exhausting 3-4 clutch fluid seats the #4 checkball and is forced through orifice #13. This orifice controls the 3-4 clutch fluid exhaust and the 3-4 clutch release rate.

The 3rd accumulator fluid exhausts from the servo assembly. The 2nd clutch fluid pressure moves the 2nd apply piston against the servo return spring force in order to move the apply pin and apply the 2-4 band.

3-2 Downshift Valve and 1-2 Upshift Checkball (#8)

The 3-4 clutch fluid exhausts from the valve and the spring force moves the valve into the second gear position. However, before the spring force overcomes the exhausting 3-4 clutch fluid pressure, the 2nd fluid feeds the 2nd clutch fluid circuit through the valve. This bypasses the control of orifice #16 at the #8 checkball and provides a faster 2-4 band apply. Remember that the #8 checkball and orifice #16 are used to help control the 2-4 band apply during a 1-2 upshift.

Downshift Timing and Control

At higher vehicle speeds, the 2-4 band apply must be delayed to allow the engine speed RPM to increase sufficiently for a smooth transfer of engine load to the 2-4 band. Therefore, exhaust of the 3rd accumulator fluid must be delayed. However, at lower speeds the band must be applied quickly. In order to provide for the varying requirements for the 2-4 band apply rate, the exhausting 3rd accumulator fluid is routed to the 3rd accumulator checkball (#2).

The exhausting 3rd accumulator fluid seats the #2 checkball and is forced through orifice #12. This fluid exhausts through the 3-4 clutch and the 3-4 signal fluid circuits and past the 2-3 shift valve. Orifice #12 slows the exhaust of the 3rd accumulator fluid and delays the 2-4 band apply rate.

After the downshift is completed, the #7 checkball unseats and allows the residual fluid in the 3rd accumulator fluid circuit to exhaust.

Remember that the PC solenoid valve continually adjusts torque signal fluid in relation to the various PCM input signals (mainly the throttle position).

Scheme 20

Manual Third Gear

A manual 4-3 downshift is available to increase vehicle performance when the use of only three gear ratios is desired. Manual Third gear range also provides engine braking in Third gear when the throttle is released. A manual 4-3 downshift is accomplished by moving the selector lever into the Manual Third (D) position. This moves the manual valve and immediately downshifts the transmission into Third gear. Refer to Overdrive Range, 4-3 Downshift for a complete description of a 4-3 downshift. In Manual Third, the transmission is prevented, both hydraulically and electronically, from shifting into Fourth gear. The following information explains the additional changes during a manual 4-3 downshift as compared to a forced 4-3 downshift.

The selector lever moves the manual shaft and manual valve into the Manual Third position (D). This allows line pressure to enter the D3 fluid circuit.

When Manual Third is selected, the PCM de-energizes the 1-2 SS valve to immediately downshift the transmission into Third gear. This electronically prevents Fourth gear.

D3 fluid pressure assists spring force to keep the valve in the downshifted position against the signal A fluid circuit. In this position, the valve blocks 3-4 signal fluid and the 4th signal fluid circuit is open to an exhaust port past the valve. Therefore, with D3 fluid pressure assisting spring force, Fourth gear is hydraulically prevented.

With the 2-3 SS valve de-energized and open, actuator feed limit (AFL) fluid acting on the 2-3 shift valve holds both valves in the upshifted position. This allows D3 fluid to feed the overrun fluid circuit through the 2-3 shift valve.

Overrun Clutch Feed Checkball (#5)

Overrun fluid pressure seats the ball against the empty D2 fluid circuit.

Overrun Clutch Control Checkball (#6)

Overrun fluid pressure seats the #6 checkball and is orificed (#20) to fill the overrun clutch feed fluid circuit. This orifice controls the overrun clutch apply rate.

4th signal fluid pressure is exhausted from the end of the 3-4 relay valve. Overrun clutch feed fluid pressure assists spring force and closes both valves. This allows overrun clutch feed fluid to flow through the 4-3 sequence valve and fill the overrun clutch fluid circuit.

Overrun Clutch Piston

Overrun clutch fluid pressure moves the piston to apply the overrun clutch plates. The overrun clutch plates provide engine compression braking in Manual Third - Third Gear.

Overrun Clutch Air Bleed Checkball

This ball and capsule is located in the overrun clutch fluid circuit in the oil pump. It allows air to exhaust from the circuit as fluid pressure increases and also allows air into the circuit to displace the fluid when the clutch releases.

Torque Converter Clutch and Torque Converter Clutch PWM Solenoid Valve

The PCM de-energizes the TCC solenoid valve and operates the duty cycle of the TCC PWM solenoid valve to release the converter clutch prior to downshifting, (assuming the converter clutch is applied in Overdrive Range-Fourth Gear when Manual Third is selected). The PCM will re-apply the converter clutch in Manual Third-Third Gear when proper driving conditions have been met.

The PC solenoid valve operates in the same manner as Overdrive Range, regulating in response to throttle position and other vehicle operating conditions.

Manual Third - First and Second Gears: Overrun Clutch Released

In Manual Third, the transmission upshifts and downshifts normally between First, Second and Third gears. However, in First and Second gears, the 2-3 SS valve is energized and the 2-3 shift valve train is in the downshifted position. The 2-3 shift valve blocks D3 fluid from entering the overrun fluid circuit and opens the overrun fluid circuit to an exhaust port at the valve. This prevents overrun clutch apply and engine compression braking in Manual Third-First and Second Gears.

Scheme 21

Manual Second Gear

A manual 3-2 downshift can be accomplished by moving the gear selector lever into the Manual Second (2) position when the transmission is operating in third gear. This causes the transmission to shift immediately into second gear regardless of vehicle operating conditions. Also, the transmission is prevented from operating in any other gear, first, third or fourth. The following information explains the additional changes during a manual 3-2 downshift, as compared to a forced 3-2 downshift. Some vehicles in manual second gear will start out in first gear, while other vehicles will have a second gear start. Refer to the owners manual for specific applications.

The selector lever moves the manual shaft and the manual valve into the manual second (2) position. This allows the line pressure to enter the D2 fluid circuit.

Third and Fourth Gears Prevented

2-3 Shift Solenoid (SS) Valve

The PCM energizes the 2-3 SS valve and the AFL fluid pressure holds the 2-3 shift valve in the downshift position. This electronically prevents operation of the third and fourth gears.

The D2 fluid is routed between the 2-3 shuttle and the 2-3 shift valves and causes the following

1. Regardless of the operating conditions, the D2 fluid pressure holds the 2-3 shift valve in the downshift position against the AFL fluid pressure.
2. The 2nd fluid is blocked from entering the 3-4 signal fluid circuit and the 3-4 signal fluid circuit is open to an exhaust port at the valve.
3. The 3-4 clutch cannot apply with the 3-4 signal fluid exhausted. Therefore, third and fourth gears are hydraulically prevented.
4. The 2nd fluid feeds the servo feed fluid circuit, but the 2nd fluid circuit has no function in manual second.
5. The AFL fluid is blocked by the 2-3 shift valve and the D432 fluid circuit is exhausted through the valve.
6. The overrun fluid is exhausted through the 2-3 shuttle valve.

The 1-2 SS valve is OFF, the signal A fluid exhausts through the solenoid and the spring force holds the valve in the upshifted position.

First Gear Prevented

The prevention of first gear is controlled electronically by the PCM through the 1-2 SS valve. The PCM keeps the 1-2 SS valve de-energized, regardless of the vehicle operating conditions when the manual shift detent lever with shaft position switch signals manual second gear range. This keeps signal A fluid exhausted and the spring force holds the 1-2 shift valve in the upshift position.

Overrun Clutch Remains Applied

Overrun Clutch Feed Checkball (#5)

Orificed D2 fluid pressure seats the #5 checkball against the empty overrun clutch fluid circuit. This is done simultaneously with the overrun clutch fluid exhausting so that there is a continuous fluid supply to the overrun clutch feed fluid circuit.

A continuous supply of fluid pressure is routed to the piston in order to keep the overrun clutch plates applied.

The converter clutch is released prior to downshifting into manual second-second gear. Under normal operating conditions, the TCC will not apply in second gear.

The PCM output signal to the PC solenoid valve increases the operating range of torque signal fluid pressure in manual second. This provides the increased line pressure for the additional torque requirements during the engine compression braking and increased engine loads.

Scheme 22

Manual First Gear

A manual 2-1 downshift can be accomplished by moving the gear selector lever into the manual first (1) position when the transmission is operating in second gear. The downshift to first gear is controlled electronically by the PCM. The PCM will not energize the 1-2 shift solenoid valve to initiate the downshift until the vehicle speed is below approximately 48 to 56 km/h (30 to 35 mph). Above this speed, the transmission operates in a manual first-second gear state. The following text explains the manual 2-1 downshift.

The selector lever moves the manual shaft and the manual valve into the manual first (1) position. This allows the line pressure to enter the Lo fluid circuit.

In both first and second gears, this solenoid is energized and maintains the signal B fluid pressure at the solenoid end of the 2-3 shift valve train.

Held in the downshift position by the signal B fluid pressure from the solenoid, the valve train blocks the AFL fluid from entering the D432 fluid circuit. The D432 fluid circuit is open to exhaust past the valve.

Below approximately 48 to 56 km/h (30 to 35 mph) the PCM energizes the normally open solenoid. This blocks the signal A fluid pressure from exhausting through the solenoid and creates the pressure in the signal A fluid circuit. Above this speed, the PCM keeps the solenoid de-energized and the transmission operates in manual first-second gear.

Signal A fluid pressure moves the valve against the spring force and into the downshift position. In this position, Lo fluid from the manual valve is routed into the Lo/1st fluid circuit and D4 fluid is blocked from entering the 2nd fluid circuit. The 2nd fluid exhausts through an orifice and an annulus exhaust port past the valve. This orifice (#26) helps control the 2-4 band release during a 2-1 downshift.

2-4 Servo Assembly

The 2nd clutch fluid, which was fed by the 2nd fluid, exhausts from the servo. This allows the spring force from the servo cushion and the servo return springs to move the 2nd apply piston and apply the pin to release the 2-4 band. These spring forces help control the 2-4 band release.

1-2 Accumulator Assembly

The 2nd clutch fluid also exhausts from the 1-2 accumulator assembly. The spring force and the accumulator fluid pressure move the accumulator piston to assist the 2nd clutch fluid exhaust.

As the accumulator fluid is filling the 1-2 accumulator assembly, the accumulator valve regulates the D4 fluid into the accumulator fluid circuit. This regulation, biased by torque signal fluid pressure and spring force, helps control the movement of the 1-2 accumulator piston. The 2nd clutch fluid exhaust, and the 2-4 band release.

1-2 Upshift Checkball (#8)

Exhausting the 2nd clutch fluid pressure unseats the ball and is routed through the 2nd fluid circuit.

Lo Overrun Valve

The Lo/1st fluid is regulated through the lo overrun valve and into the Lo/reverse fluid circuit in order to control the lo and reverse clutch apply.

Lo and Reverse Piston

The Lo/reverse fluid pressure acts on the inner area of the piston in order to move the piston and in order to apply the lo and reverse clutch plates.

Overrun Clutch Applied

The overrun clutch remains applied in manual first in order to provide engine compression braking.

Similar to manual second, the PCM output signal to the PC solenoid valve increases the operating range of the torque signal fluid pressure. This provides the increased line pressure for the additional torque requirements during the engine compression braking and the increased engine loads.

Scheme 23

Scheme 24

Scheme 25

Scheme 26

Scheme 27

Scheme 28

Scheme 29

Scheme 30

Scheme 31

Scheme 32

See also:
• Transmission Fluid Temperature Sensor Specifications
• Electronic Component Description
• Overdrive Range, Fourth Gear - Torque Converter Clutch Applied
• Overdrive Range, 4-3 Downshift