Honda Civic. Manual — part 177

The regulator valve maintains constant hydraulic pressure from the ATF pump to
the hydraulic control system. While also furnishing fluid to the lubrication 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 toward the spring, 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 the 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.

Fig. 36: Regulator Valve Operation Diagram
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Increases in hydraulic pressure according to torque are regulated 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.

2008 Honda Civic LX

2006-08 TRANSMISSION Automatic Transmission - Civic (Except Hybrid)

Fig. 37: Identifying Regulator Spring Cap
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Servo Body

The servo body is on the main valve body. The servo body contains the servo valve,
shift valve B, cut valve A, the accumulators for 2nd, 4th, and 5th, and shift solenoid
valves A, B, C, and D.

Fig. 38: Identifying Servo Body Components
Courtesy of AMERICAN HONDA MOTOR CO., INC.

2008 Honda Civic LX

2006-08 TRANSMISSION Automatic Transmission - Civic (Except Hybrid)

Accumulator

The accumulators are located in the regulator valve body and the servo body. The
regulator valve body contains the 1st and 3rd accumulators, and the servo body
contains the 2nd, 4th, and 5th accumulators.

Fig. 39: Identifying Accumulator Components
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Hydraulic Flow

Distribution of Hydraulic Pressure

As the engine turns, the ATF pump starts to operate. Automatic transmission fluid
(ATF) is drawn through the ATF strainer (filter) and discharged into the hydraulic
circuit. Then, ATF flowing from the ATF pump becomes line pressure that is
regulated by the regulator valve. Torque converter pressure from the regulator valve
enters the torque converter through the lock-up shift valve, and it is discharged from
the torque converter. The torque converter check valve prevents torque converter
pressure from rising.

The PCM turns the shift solenoid valves ON and OFF. The shift solenoid valve
controls line pressure from the ATF pump via the manual valve when the shift

2008 Honda Civic LX

2006-08 TRANSMISSION Automatic Transmission - Civic (Except Hybrid)

solenoid valve is OFF. When the shift solenoid valve is turned ON by the PCM,
line pressure changes to shift solenoid valve pressure at the shift solenoid valve,
then the shift solenoid valve pressure flows to the shift valve. Applying shift
solenoid pressure to the shift valve moves the position of the shift valve, and
switches the port of the hydraulic circuit. The PCM also controls A/T clutch
pressure control solenoid valves A, B, and C. The A/T clutch pressure control
solenoid valves regulate hydraulic pressure, and apply the pressure to the clutches
to engage smoothly. The clutches receive optimum clutch pressure which is
regulated by the A/T clutch pressure control solenoid valves for comfortable driving
and shifting under all conditions.

Hydraulic Pressure at the Port for use in the hydraulic circuit

HYDRAULIC PRESSURE REFERENCE

Port No.

Hydraulic

Pressure

Port No.

Hydraulic

Pressure

1

Line

5T

A/T clutch
pressure control
solenoid valve C

3

Line

SA

Shift solenoid
valve A

3'

Line

SB

Shift solenoid
valve B

4

Line

SC

Shift solenoid
valve C

4'

Line

SD

Shift solenoid
valve D

4"

Line

10

1st clutch

7

Line

20

2nd clutch

1A

Line

30

3rd clutch

1B

Line

40

4th clutch

1C

Line or A/T clutch
pressure control
solenoid valve A

50

5th clutch

2008 Honda Civic LX

2006-08 TRANSMISSION Automatic Transmission - Civic (Except Hybrid)