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AUTOMATIC TRANSAXLE
AUTOMATIC TRANSAXLEAT±1
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MEMO
AUTOMATIC TRANSAXLEAT±2
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A140L AND A140E
AUTOMATIC TRANSAXLE
AUTOMATIC TRANSAXLEAT±3
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DESCRIPTION
The A140L and. A140E automatic transaxle described in this AT section is a lock±up four±speed automat-
ic transaxle developed exclusively for use± with a transversely±mounted engine.
The A140E is called an ECT (Electronic Controlled Transaxle). Based on the A140L, the hydraulic control
system has been changed, and the shift and lock±up timing are controlled by micro computer.
The construction and operation of the A140L, will first be explained. Then the difference between the
A140E
and the A140L, and the features of the ECT, will also be explained.
± AUTOMATIC TRANSAXLEDescription (A140L and A140E )AT±4
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A140L Automatic Transaxle
CONSTRUCTION AND OPERATION
The A140L automatic transaxle can be roughly divided into the automatic transmission section and the
differential section. The automatic transmission section is composed of the torque converter, planetary
gear unit and the hydraulic control system.
OPERATION
The pump impeller is rotated by the engine, which
causes a flow in the ATF inside the torque converter.
The flow of ATF caused by the pump impeller strikes
the turbine runner, providing a force to rotate the tur-
bine runner, and transmits torque to the input shaft.
The flow of ATF which has hit the turbine runner re-
bounds and tries to flow in the direction opposite to
the direction of rotation of the pump impeller, but the
stator returns the flow the original direction of rotation.
So the ATF
becomes a force which supports the pump impeller
and increases torque.
HINT: Although the stator is immobilized by the one-
way clutch, should the one±way clutch become de-
fective the stator will be rotated by the flow of ATF,
the flow of
ATF will not be reversed, torque will not be increased
and the problem of inadequate acceleration will occur.
The lock±up clutch is pushed against the front cover
by fluid pressure so that the engine revolutions are
directly transmitted to the input shaft without the me-
dium of the
AT F.
1. Torque Converter
CONSTRUCTION
The torque converter is composed of the pump impeller
which is rotated by the engine, the turbine runner and
lock±up clutch which are fixed to the transmission input
shaft, and the stator which is attached to the stator
shaft via the one±way clutch.
The torque converter is filled with ATF.
± AUTOMATIC TRANSAXLEDescription (A140L and A140E)AT±5
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2. Planetary Gear Unit
CONSTRUCTION
The planetary gear unit is composed of three sets of planetary gears, three clutches which transmit
power to the planetary gears, and four brakes and three one±way clutches which immobilize the
planetary carrier and planetary sun gear.
± AUTOMATIC TRANSAXLEDescription (A140L and A140E)AT±6
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OPERATION
Power from the engine transmitted to the input shaft via the torque converter is then trans-
mitted to the planetary gears by the operation of the clutch.
By operation of the brake and one±way clutch, either the planetary carrier or the planetary sun
gear are immobilized, altering the speed of revolution of the. planetary gear unit.
Shift change is carried out by altering the combination of clutch and brake operation.
Each clutch and brake operates by hydraulic pressure; gear position is decided according to
the throttle opening angle and vehicle speed, and shift change automatically occurs.
The conditions of operation for each gear position are shown on the following illustrations:
± AUTOMATIC TRANSAXLEDescription (A140L and A140E)AT±7
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3. Hydraulic Control System
CONSTRUCTION
The hydraulic control is composed of an oil pump, rotated by the engine, which supplies hydraulic pres-
sure; a valve body which controls the hydraulic pressure and the opening and closing of the fluid pas-
saged; and a governor valve which supplies hydraulic pressure in accordance with vehicle speed.
OPERATION
Hydraulic pressure supplied by the oil pump is controlled± by the regulator valve; the resulting oil pres-
sure controlled by the regulator valve is called the line pressure.
Line pressure produces the hydraulic pressure for throttle pressure and governor pressure. Also, line
pressure produces hydraulic pressure for the operation of each brake and clutch in the planetary gear
unit.
The throttle valve acts to produce hydraulic pressure, called the throttle pressure, which responds to ac-
celerator pedal modulation. Throttle pressure increases as the accelerator pedal is depressed.
The governor valve produces hydraulic pressure, called the governor pressure, in response to vehicle
speed. Governor pressure increases as vehicle speed increases.
In accordance with the difference between throttle pressure and governor pressure, each shift valve
shifts, the fluid passages to the clutches are brakes in the planetary gear unit are opened and the
clutches and brakes operate, and shift change occurs.
The operation of the hydraulic control system, using the 2±3 shift valve as an example, is shown below;
± AUTOMATIC TRANSAXLEDescription (A140L and A140E)AT±8