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 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 below the dashboard, under the front lower panel behind the center console.

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, D, E, CPC valve C, the relief valve, the lock-up shift valve, the lock-up timing valve, the lubrication control valve, the lubrication and the ATF pump gears. The secondary valve body contains shift valve C, CPC valves A, B, the reverse CPC valve, the servo control valve, and the kick-down valve. The regulator valve body contains the regulator valve, the cooler check valve, 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. All the clutches receive fluid from the internal hydraulic circuit.

Shift Control Mechanism
To shift gears, the PCM controls shift solenoid valves A, B, and C, and automatic transmission (A/T) clutch pressure control solenoid valves A and B, 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 and B control CPC valves A and B to shift smoothly between lower gear and higher gear. This pressurizes 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 with sequential shift (M position) (3rd, 4th, and 5th). 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 lock-up control valve and the lock-up timing valve control the range of lockup according to A/T clutch pressure control solenoid valve C. Shift solenoid valve D is located on the accumulator body in the transmission, 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 five positions; P: PARK, R: REVERSE, N: NEUTRAL, D: DRIVE 1st through 5th gear range with automatic shift and sequential shift in M (sequential shift mode) position, and L: LOW 1st and 2nd gear range with automatic shift.





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. With the shift lever in the M (sequential shift mode) position, the shift indicator in the gauge control module will display the gear selected.

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 1st gear in the M 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 L position. However, the one-way clutch disengages when the 2nd, 3rd, 4th, or 5th clutches and gears are applied in the D or L 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

Transmission Cutaway View:

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.

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 on the secondary shaft.

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.





In 1st gear in M position (Acceleration)
In the 1st gear in the M 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.





In 1st gear in M Position (Deceleration)
The power flow in the 1st gear in the M 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 L Position
In the D position, the optimum gear is a automatically selected from the 1st, 2nd, 3rd, 4th, and 5th gears (in the D position); 1st and 2nd gears (in the L position) according to conditions such as the balance between the throttle opening (engine loading) and vehicle speed.

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.





In 2nd Gear
^ 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.





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.





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 and L 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.