Part 1

System Description

General Operation
The automatic transmission is a combination of a 3-element torque converter and four-shaft electronically controlled unit which provides 5 speeds forward and 1 reverse. The entire unit is positioned in line with the engine.

Torque Converter, Shafts, Gears, and Clutches
The torque converter consists of a pump, turbine, and stator assembly in a single unit. The converter housing (pump) is connected to the engine crankshaft and turns as the engine turns. Around the outside of the torque converter is a ring gear which meshes with the starter pinion when the engine is being started. The entire torque converter assembly serves as a flywheel, transmitting power to the transmission mainshaft. The transmission has four parallel shafts: the mainshaft, the countershaft, the secondary shaft, and the intermediary shaft. The mainshaft is in line with the engine crankshaft. The mainshaft includes the 4th and 5th clutches, and gears for 3rd, 4th, 5th, and reverse (reverse gear is integral with the 5th gear). The countershaft includes gears for the final drive, 2nd, idler, 1st, 4th, 5th, and reverse (the final drive gear is integral with the countershaft). The secondary shaft includes the 1st, 1st-hold, and 2nd clutches, and gears for park, 2nd, idler, and 1st. The intermediary shaft includes the 3rd clutch, and gears for 3rd and 4th. The countershaft 5th gear and the countershaft reverse gear can be locked to the countershaft at its left end, providing 5th gear or reverse, depending with which way the selector is moved. The gears on the mainshaft, secondary shaft, and intermediary shaft are in constant mesh with those on the countershaft, When certain conditions of gears in the transmission are engaged by the clutches, power is transmitted through the mainshaft, to the secondary shaft or the intermediary shaft, then to the countershaft or through the mainshaft to the countershaft to provide drive.

Electronic Control
The electronic control system consists of the powertrain control module (PCM), sensors, and seven solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions. The PCM is located in the engine compartment.

Hydraulic Control
The valve bodies include the main valve body, the secondary valve body, the regulator valve body, and the accumulator body. They are bolted to the torque converter housing. The main valve body contains the manual valve, the modulator valve, the torque converter check valve, shift valves A, B, E, CPC valve A, the servo control valve, the relief valve, the lock-up shift valve, the lock-up timing valve, the lubrication control valve, the lubrication check valve, and the ATF pump gears. The secondary valve body contains shift valve C, D, CPC valve B, C, the reverse CPC valve, and the reverse control valve. The regulator valve body contains the regulator valve, the cooler check valve, the air check bolts, the lock-up control valve, and the 3rd accumulator. The accumulator body contains the 1st, 1st-hold, 2nd, 4th, and 5th accumulators, shift solenoid valves A, B, C, and D. Fluid from the regulator, passes through the manual valve to the various control valves. The all clutches receive fluid from the internal hydraulic circuit.

Shift Control Mechanism
To shift gears, the PCM controls shift solenoid valves A, B, C, and D, and automatic transmission (A/T) clutch pressure control solenoid valves A, B, and C, while receiving input signals from various sensors and switches located throughout the vehicle. The shift solenoid valves shift the positions of the shift valves to switch the port to send hydraulic pressure to the clutches. A/T clutch pressure control solenoid valves A, B, and C control CPC valve A, B, and C to shift smoothly between lower gear and higher gear. This pressurize a line to one of the clutches, engaging the clutch and its corresponding gear.

Lock-up Mechanism
The lock-up mechanism operates in the D position (2nd, 3rd, 4th, and 5th), and D position D3 driving mode (2nd and 3rd). The pressurized fluid is drained from the back of the torque converter through a fluid passage, causing the torque converter clutch piston to be held against the torque converter cover. As this takes place, the mainshaft rotates at the same speed as the engine crankshaft. Together with hydraulic control, the PCM optimizes the timing of the lock-up mechanism. When shift solenoid valve D activates, modulator pressure changes to switch lock-up on and off. The lockup control valve and the lock-up timing valve control the volume of lock-up according to A/T clutch pressure control solenoid valve C. Shift solenoid valve D is mounted on the accumulator body, and A/T clutch pressure control solenoid valve C is mounted on the transmission housing. They are all controlled by the PCM.

Gear Selection
The shift lever has six positions; P: PARK, R: REVERSE, N: NEUTRAL, D: DRIVE 1st through 5th gear ranges, and 1st through 3rd gear ranges with D3 driving mode, 2: 2nd gear, and 1: 1st gear.





Starting is possible only in the P and N positions because of a slide-type neutral-safety switch.

Automatic Transmission (A/T) Gear Position Indicator
The A/T gear position indicator in the instrument panel shows which shift lever position has been selected without having to look down at the shift lever.

Clutches
The 5-speed automatic transmission uses hydraulically-actuated clutches to engage or disengage the transmission gears. When hydraulic pressure is introduced into the clutch drum, the clutch piston moves. This presses the friction discs and steel plates together, locking them so they don't slip. Power is then transmitted through the engaged clutch pack to its hub-mounted gear. Likewise, when the hydraulic pressure is bled from the clutch pack, the piston releases the friction discs and the steel plates, and they are free to slide past each other. This allows the gear to spin independently on its shaft, transmitting no power.

1st Clutch
The 1st clutch engages/disengages 1st gear, and is located at the left end of the secondary shaft. The 1st clutch is supplied hydraulic pressure by its ATF feed pipe within the secondary shaft.

1st-hold Clutch
The 1st-hold clutch engages/disengages 1st-hold in 1 position, and is located in the 1st clutch drum. The 1st-hold clutch is supplied hydraulic pressure by its ATF feed pipe within the secondary shaft.

2nd Clutch
The 2nd clutch engages/disengages 2nd gear, and is located at the right end of the secondary shaft. The 2nd clutch is supplied hydraulic pressure through the secondary shaft by a circuit connected to the internal hydraulic circuit.

3rd Clutch
The 3rd clutch engages/disengages 3rd gear, and is located at the end of the intermediary shaft. The 3rd clutch is supplied hydraulic pressure through the intermediary shaft by a circuit connected to the internal hydraulic circuit.

4th Clutch
The 4th clutch engages/disengages 4th gear, and is located at the middle of the mainshaft. The 4th clutch is joined back-to-back to the 5th clutch. The 4th clutch is supplied hydraulic pressure through the mainshaft by a circuit connected to the internal hydraulic circuit.

5th Clutch
The 5th clutch engages/disengages 5th gear, as well as reverse gear, and is located at the middle of the mainshaft. The 5th clutch is joined back-to-back to the 4th clutch. The 5th clutch is supplied hydraulic pressure through the mainshaft by a circuit connected to the internal hydraulic circuit.

One-way Clutch
The one-way clutch is positioned between the 1st clutch hub and the secondary shaft 1st gear. The secondary shaft 1st gear is splined to the 1st-hold clutch hub, with the 1st-hold clutch hub splined to the secondary shaft. The secondary shaft 1st gear provides the outer race surface, and the 1st clutch hub provides the inner race surface. The one-way clutch locks when power is transmitted from the secondary shaft 1st gear to the countershaft 1st gear. The 1st clutch and gears remain engaged in the 1st, 2nd, 3rd, 4th, and 5th gear ranges in the D, or 2 position. However, the one-way clutch disengages when the 2nd, 3rd, 4th, or 5th clutches and gears are applied in the D, or 2 position. This is because the increased rotational speed of the gears on the secondary shaft causes the one-way clutch to free-wheel with the 1st clutch still engaged.

Power Flow

Gear Operation
Gears on the mainshaft:
^ 4th gear is engaged/disengaged with the mainshaft by the 4th clutch.
^ 5th gear is engaged/disengaged with the mainshaft by the 5th clutch.
^ Reverse gear is engaged/disengaged with the mainshaft by the 5th clutch.
^ 3rd gear is splined with the mainshaft and rotates with the mainshaft.
Gears on the countershaft:
^ Final gear is integral with the countershaft.
^ 1st gear, 2nd gear, and 4th gear are splined with the countershaft, and rotate with the countershaft.
^ 5th gear and reverse gear rotate freely from the countershaft. The reverse selector engages 5th gear and reverse gear with the reverse selector hub. The reverse selector hub is splined to the countershaft so 5th gear and reverse gear engage with the countershaft.
^ Idler gear is located over the 2nd gear, and rotates freely from the countershaft.
Gears on the secondary shaft:
^ 1st gear is engaged/disengaged with the secondary shaft by the 1st clutch. 1st gear is engaged with the secondary shaft by the one-way clutch and the 1st-hold clutch when decelerating for engine braking.
^ 2nd gear is engaged/disengaged with the secondary shaft by the 2nd clutch.
^ Idler gear is splined with the secondary shaft, and rotates with the secondary shaft.
^ Park gear is integral with the 2nd gear.
Gears on the intermediary shaft:
^ 3rd gear is engaged/disengaged with the intermediary shaft by the 3rd clutch.
^ 4th gear is splined with the intermediary shaft.

Transmission Cutaway View





P Position
Hydraulic pressure is not applied to the clutches. Power is not transmitted to the countershaft. The countershaft is locked by the park pawl interlocking the park gear.

N Position
Engine power transmitted from the mainshaft drives the mainshaft 3rd gear, the intermediary shaft 3rd gear, but hydraulic pressure is not applied to the clutches. Power is not transmitted to the countershaft. In this position, the position of the reverse selector differs according to whether the shift lever shifted from the D or R position:
^ When shifted from the D position, the reverse selector engages with the countershaft 5th gear and the reverse selector hub, and the 5th gear engages with the countershaft.
^ When shifted from the R position, the reverse selector engages with the countershaft reverse gear, and the reverse selector hub, and the reverse gear engages with the countershaft.





1 Position (Acceleration)
In the 1 position under an acceleration, hydraulic pressure is applied to the 1st clutch and the 1st-hold clutch. The power flow when accelerating is as follows:
^ Hydraulic pressure is applied to the 1st clutch, then the 1st clutch engages the secondary shaft 1st gear with the secondary shaft by the one-way clutch.
^ The mainshaft 3rd gear drives the secondary shaft via the countershaft idler gear and secondary shaft idler gear.
^ The secondary shaft 1st gear drives the countershaft 1st gear and the countershaft.
^ Hydraulic pressure is also applied to the 1st-hold clutch, and the 1st-hold clutch engages the secondary shaft 1st gear with the secondary shaft.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.





1 Position (Deceleration)
The power flow in the 1 position when decelerating is as follows:
^ Hydraulic pressure is applied to the 1st clutch and the 1st-hold clutch.
^ Rolling resistance from the road surface goes through the front wheels to the final driven gear, then to the countershaft idler gear.
^ The one-way clutch disengages because the application of torque is reversed.
^ The force conveyed to the secondary shaft idler gear turns the mainshaft 3rd gear via the countershaft idler gear. As a result, engine braking can be obtained with 1st gear.





D or D3 Position D3 Driving Mode
In the D position, the optimum gear is automatically selected from the 1st, 2nd, 3rd, 4th, and 5th gears (in the D position); 1st, 2nd, and 3rd gears (in the D position D3 driving mode) according to conditions such as the balance between the throttle opening (engine loading) and vehicle speed.

D Position in 1st Gear
^ Hydraulic pressure is applied to the 1st clutch, then the 1st clutch engages the secondary shaft 1st gear with the secondary shaft by the one-way clutch.
^ The mainshaft 3rd gear drives the secondary shaft via the countershaft idler gear and the secondary shaft idler gear.
^ The secondary shaft 1st gear drives the countershaft 1st gear and the countershaft.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.





D Position in 2nd Gear and 2 Position
^ Hydraulic pressure is applied to the 2nd clutch, then the 2nd clutch engages the secondary shaft 2nd gear with the secondary shaft.
^ The mainshaft 3rd gear drives the secondary shaft via the countershaft idler gear and the secondary shaft idler gear.
^ The secondary shaft 2nd gear drives the countershaft 2nd gear and the countershaft.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.
^ Hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of 2nd gear exceeds that of 1st gear, power from 1st gear is cut off at the one-way clutch.





D Position in 3rd Gear
^ Hydraulic pressure is applied to the 3rd clutch, then the 3rd clutch engages the intermediary shaft 3rd gear with the intermediary shaft.
^ The mainshaft 3rd gear drives the intermediary shaft 4th gear via the intermediary shaft 3rd gear and the 3rd clutch.
^ The intermediary shaft 4th gear drives the countershaft 4th gear and the countershaft via the mainshaft 4th gear.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.
^ Hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of 3rd gear exceeds that of 1st gear, power from 1st gear is cut off at the one-way clutch.





D Position in 4th Gear
^ Hydraulic pressure is applied to the 4th clutch, then the 4th clutch engages the mainshaft 4th gear with the mainshaft.
^ The mainshaft 4th gear drives the countershaft 4th gear and the countershaft.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.
^ Hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of 4th gear exceeds that of 1st gear, power from 1st gear is cut off at the one-way clutch.





D Position in 5th Gear
^ Hydraulic pressure is applied to the servo valve to engage the reverse selector with the countershaft 5th gear while the shift lever in the forward range (D, 2, and 1 positions).
^ Hydraulic pressure is applied to the 5th clutch, then the 5th clutch engages the mainshaft 5th gear with the mainshaft.
^ The mainshaft 5th gear drives the countershaft 5th gear, which drives the reverse selector hub and the countershaft.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.
^ Hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of 5th gear exceeds that of 1st gear, power from 1st gear is cut off at the one-way clutch.





R Position
^ Hydraulic pressure is applied to the servo valve to engage the reverse selector with the countershaft reverse gear while the shift lever is in the R position.
^ Hydraulic pressure is applied to the 5th clutch, then the 5th clutch engages the mainshaft reverse gear with the mainshaft.
^ The mainshaft reverse gear drives the countershaft reverse gear via the reverse idler gear.
^ The countershaft reverse gear drives the countershaft via the reverse selector which drives the reverse selector hub.
^ The rotation direction of the countershaft is changed by the reverse idler gear.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.





Electronic Control System

Functional Diagram
The electronic control system consists of the powertrain control module (PCM), sensors, and the solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions.
The PCM receives input signals from the sensors, switches, and the other control units, processes data, and the outputs signals for the engine control system and the Art- control system. The A/T control system includes shift control, grade logic control, clutch pressure control, and the lock-up control. The PCM switches the shift solenoid valves and the A/T clutch pressure control solenoid valves to control shifting transmission gears and the lock-up torque converter clutch.





Electronic Controls Locations

Electronic Controls Component Location Index:

Shift Control
The PCM instantly determines which gear should be selected by various signals sent from sensors and switches, and it actuates shift solenoid valves A, B, C, and D to control shifting transmission gear.
The shift solenoid valves have two types:
^ Shift solenoid valves A and D use ON-OPEN/OFF-CLOSE type; shift solenoid valve opens the port of shift solenoid valve pressure while shift solenoid valve is turned ON by the PCM, and closes the port when shift solenoid valve is OFF.
^ Shift solenoid valves B and C use ON-CLOSE/OFF-OPEN type; shift solenoid valve closes the port of shift solenoid valve pressure while shift solenoid valve is turned ON by the PCM, and opens the port when shift solenoid valve is OFF.
The combination of driving signals to shift solenoid valves A, B, C, and D are shown in the table.





Shift Control - Grade Logic Control
The grade logic control system has been adopted to control shifting in the D position. To control shifting while the vehicle is ascending or descending a slope the PCM compares actual driving conditions with programmed driving conditions, based on the input from the accelerator pedal position sensor, the engine coolant temperature sensor, the barometric pressure sensor, the brake pedal position switch signal, and the shift lever position signal.





Grade Logic Control: Ascending Control
When the PCM determines that the vehicle is climbing a hill in the D position, the system extends the engagement area of 2nd gear, 3rd gear, and 4th gear to prevent the transmission from frequently shifting between 2nd and 3rd gears, between 3rd and 4th gears, and between 4th and 5th gears, so the vehicle can run smooth and have more power when needed.

NOTE: Shift commands stored in the PCM between 2nd and 3rd gears, between 3rd and 4th gears, and between 4th and 5th gears, enable the PCM to automatically select the most suitable gear according to the magnitude of a gradient.





Grade Logic Control: Descending Control
When the PCM determines that the vehicle is going down a hill in the D position, the shift-up speed from 4th to 5th gear, 3rd to 4th gear, and from 2nd to 3rd (when the throttle is closed) becomes faster than the set speed for flat road driving to widen the 4th gear, 3rd gear, and 2nd gear driving areas. This, in combination with engine braking from the deceleration lock-up, achieves smooth driving when the vehicle is descending. There are three descending modes with different 4th gear driving areas, 3rd gear driving areas, and 2nd gear driving areas according to the magnitude of a gradient stored in the PCM. When the vehicle is in 5th or 4th gear and you are decelerating while applying the brakes on a steep hill, the transmission will downshift to a lower gear. When you accelerate, the transmission will then return to a higher gear.





Clutch Pressure Control
The PCM actuates A/T clutch pressure control solenoid valves A, B, and C to control the clutch pressure. When shifting between gears, the clutch pressure regulated by A/T clutch pressure control solenoid valves A, B, and C engages and disengages the clutch smoothly.
The PCM receives input signals from the various sensors and switches, processes data, and outputs current to A/T clutch pressure control solenoid valves A, B, and C.





Lock-up Control
The shift solenoid valve D controls the hydraulic pressure to switch the lock-up shift valve and lock-up ON and OFF. The PCM actuates shift solenoid valve D and A/T clutch pressure control solenoid valve C ON, the condition of lock-up starts. The A/T clutch pressure control solenoid valve C regulates and apply the hydraulic pressure to the lock-up control valve to control the volume of the lock-up.
The lock-up mechanism operates in the D position (2nd, 3rd, 4th, and 5th), and in the D position with D3 driving mode (2nd and 3rd).





PCM A/T Control System Electrical Connections

PCM A/T Control System Electrical Connections:

PCM A/T Control System Inputs and Outputs

PCM A/T Control System Inputs and Outputs (Part 1):

PCM A/T Control System Inputs and Outputs (Part 2):

PCM A/T Control System Inputs and Outputs (Part 3):

PCM A/T Control System Inputs and Outputs (Part 4):

Hydraulic Controls
The valve body includes the main valve body, the regulator valve body, the secondary valve body, and the accumulator body. The ATF pump is driven by splines on the end of the torque converter which is attached to the engine. Fluid flows through the regulator valve to maintain specified pressure through the main valve body to the manual valve, directing pressure to each of the clutches. Shift solenoid valves A, B, C, and D are mounted on the accumulator body. A/T clutch pressure control solenoid valves A, B, and C are mounted on the transmission housing.





Main Valve Body
The main valve body contains the manual valve, the modulator valve, shift valve A, shift valve B, shift valve E, CPC valve A, the servo control valve, the lubrication check valve, the lubrication control valve, the torque converter check valve, the lock-up timing valve, the relief valve, the lock-up shift valve, and the ATF pump gears. The primary function of the main valve body is to switch fluid pressure on and off to control hydraulic pressure going to the hydraulic control system.





Regulator Valve Body
The regulator valve body is located on the main valve body. The regulator valve body contains the regulator valve, the cooler check valve, the air check bolts, the lock-up control valve, the servo valve, and the 3rd accumulator.





Regulator Valve
The regulator valve maintains constant hydraulic pressure from the ATF pump to the hydraulic control system, while also furnishing fluid to the lubricating system and the torque converter. Fluid from the ATF pump flows through B and B'. Fluid entering from B flows through the valve orifice to the A cavity. This pressure of the A cavity pushes the regulator valve to the spring side, and this movement of the regulator valve uncovers the fluid port to the torque converter and the relief valve. The fluid flows out to the torque converter and the relief valve, and the regulator valve returns under spring force. According to the level of hydraulic pressure through B, the position of the regulator valve changes, and the amount of fluid from B' through the torque converter changes. This operation is continued, maintaining the line pressure.





Increases in hydraulic pressure according to torque are performed by the regulator valve using stator torque reaction. The stator shaft is splined to the stator in the torque converter, and its arm end contacts the regulator spring cap. When the vehicle is accelerating or climbing (torque converter range), stator torque reaction acts on the stator shaft, and the stator arm pushes the regulator spring cap in the direction of the arrow in proportion to the reaction. The stator reaction spring compresses, and the regulator valve moves to increase the line pressure which is regulated by the regulator valve. The line pressure reaches its maximum when the stator torque reaction reaches its maximum.