1977 DATSUN PICK-UP ECO

The
model
3N7l
B
automatic

trans

mission
is

a

fully
automatic

unit
con

sisting
primarily
of
3
element

hydrau

lic

torque
converter
and

two

planetary

gear
sets
Two

multiple
disc
clutches
a

multiple
disc
brake
a
band
brake
and

a
one

way

sprag
clutch

provide
the

friction
elements

required
to
obtain

the
desir
d
function
of
lhe
two

plane

tary
gear
sets

The

two

planetary
gear
sets

give

three
forward
ratios

and
one
reverse

Changing
of
the

gear
ratios
is

fully

automatic
in
relation
to
vehicle

speed

and

engine
torque
input
V

chide

speed

and

engine
manifold
vacuum

signals

are

constantly
fed
to
the

transmission

to

provide
the

proper
gear
ralio
for

maximum

efficiency
and

performance

at
all
throttle

openings

The
model
3N71
B
has
six

selector

1

9sition
LP
R

N
D
2
1

I

Park

position
positively
locks

the

output
shaft
to

the
transmission

case

by
means
of
a

locking

pawl
to

prevent
the
vehicle
from

rolling
in

either
direction

This

position
should
be

selected

whenever
the
driver
leaves
Ihe
vehicle

Thc

engine

may
be
slarted
in
Park

position

R
Reverse

range
enables
the

vehicle
to
be

operated
in

a
reverse

direction

N
Neutral

position
enables
the

engine
to

be
started
and
run

without

driving
the
vehicle

0
Drive

range
is
used

for
all

normal

driving
conditions

Drive

range
has
three

gear
ratios

from
the

starting
ratio

to
direct
drive
Automatic
Transmission

DESCRIPTION

2

2

range
provides

performance

for

driving
on

slippery
surfaces

2

range
can
also
be
used
for

engine

braking

2

range
can
be
selected
at

any

vehicle

speed
and

prevents
the
trans

mission
from

shifting
out
of

second

gear

I
I

range
can
be

selected
at

any
vehicle

speed
and
the
transmission

will
shift
to

second

gear
and
remain
in

second
until
v

hicle

speed
is
reduced

10

approximately
40
to
50

kmfh
25

to
30
MPH

I

range
position
prevents
the

transmission
from

shifting
out
of
low

gear
This
is

particularly
beneficial
for

maintaining
maximum

engin
braking

when

continuous
low

gear
operation
is

desirable

The

torque
converter

assembly
is
of

welded

construction
and
can

nOlbe

disassembled

for
service

FLUID
RECOMMENDATION

Use
automatic
transmission

fluid

having
DEXRON
identifications

only
in
the
3N71
B

automatic
transmis

sion

IDENTIFICATioN
NUMBER

Stamped

position

The

plate
is

attached
to
the

right

hand

side
of
transmission
case

as

shown
io

Figure
AT

I

AT
2
AT344

Fig
AT
I

Identification
number

Identification

of
number

Arrangements

See
below

Model
code

JAPAN

AUTOMATIC

0J
TRANSMISSION
CO
LTD

I
MODEL
X2402

I

J
I
NO

4912345

I

Unit
number

Number

designation

4
9

I

234
5

L

Serial

production

number
for

the
month

Month
of

production

X

Oct
Y

Nov
Z
Dec

last

figure
denoting

the

year
A
D

plate
The

parking
rod

pin
operates
the

rod
at
p

range
and

operates
the

mechanical

lock

system

The

above
described
manual
shaft
is

further

equipped
with

an
inhibitor

switch
A

rotor

inside
the

inhibitor

switch

rotates
in

response
to
each

range
When
tne

range
is

selected
at

p
or

N
the
rotor

closes
the

starter

magnet
circuit

so
that
the

engine
can
be
started
When
the

range

is

selected
at
R
the
rolor
closes
the

back

up

lamp
circuit
and
the
back

up

lamp

lights

CD

1
Manual

pia
te

2
Inhibitor

switch
ATOB7

Parking
rod

Manual
shaft

Fig
AT
4

Manual

linkage

VACUUM

DIAPHRAGM

The

vacuum

diaphragm
is

installed

on
the
left

center

portio
n
of
the

transmission

case
The

internal
con

struction
of
the

vacuum

diaphragm
is

as
follows

A
rubber

diaphragm
forms
a

parti

tion
in
the

center
The

engine
intake

manifold

negative
pressure

l
led

through
a

vacuum
tube
and

spring

force
is

applied
to
the
front
surfaceof

the
rubber

diaphragm
while

atmos

pheric

pressure
is

applied
to
the
back

surface
The
difference

between

pres

sure

applied
to
the
front
and
ba
K

I

surfaces
causes
a

vacuum
reactIOn

which
activates
the
throttle
valve
of

the
control
valve
inside
the
transrhis

sion

case

Wheri
accelerator

pedal
is

fully
de

pressed
and
the
buretor
is

fU

IIy

opened
but
th

engirie

sp
eed
is

not

suificientl
increased
the

manifold

negative
plre
sure
lowers

Le
tends

towards

atmospheric

pressure
and
the
Automatic

Transmission

vacuum
reaction
increases
since

the

flow

velocity
of
mixture
inside
the

intake
m
mifold
is
slow

Contrarily

when
the

engine
speed
increases
and

the
flow

velocity
of
the

mixture
in

creases
or

when
the
carburetor

is

closed

the
manifold

negative

pressure

increases
Le
tends

towards
vacuum

and
the

vacuum
reaction
is

reduced

Thus
a

signal
to

genera
Ie

hydraulic

pressure
P
rfe

tly
suited
to
the

engine

loading
at

trye
control
valve
is

trans

mitted
from
the
vacuum

diaphragm

and
the
most
suitable

timing
for

speed

change
and
lin
e

pressure
is
obtaine

so

that
the

most

proper
torque
capacity

is

obtained

against
the

transmitting

torque

To
inl
lkc

manifold

AT088

Fig
AT
5
Vacuum

diaphragm

DOWNSHIFT

SOLENOID

T
e

downshift
solenoid
is

of
a

magnetic
type
installed
on

the
left
re
r

portion
of
the
transmission

case
When

a
driver

requires

accelerating
power

and

dePresses
the

accelerator

pedal

down

to
the

stopper
a
kickdown

switch

19ca
ted
in
the

middle
of

the

accelerator

link
is

depressed

by
a

push

rod
he

kickdown
switch

doses
cur

rent
flows
to

the
solenoid

the
sole

noid

push
rod
is

depressed
the
down

shift
valve
of
the

control
valvc
insidc

the

transmi
ssion

case
is

depressed
nd

the

speed
is

changed
forcedly
fmm

3rd
to
2nd
within
a
cerlaill

vehi

cle

speed
limit

Note
Since
theki

kdown
switch

closes
when
the
accelerator

pedal
is

d

epr
ssed
from

7

i
t
I
S
I
6

of
tiie

whole

stroke
the
a
ccel
rator

ped
1

should

be
correctly

adjusted
so
as

arf

rd
a

omplete
stro

e
I

The

arrangement
of
the
swit

h

wries

ccording
m

eI

AT

S
c
C

r
11
I

Kickdown

h

switch

Dowri

shift
solenoid

AT089

Fig
AT
6

Downshifl80lenoid

GOVERNER

VALVE

The

primary
and

secondary

gover

nor
valves
are
installed

separately
on

the

back
of
the
oil
distributor

on
the

transmission

outp
t

sha
ft

tn

y
op

erate

al
the
same

speed
as
th
ar

iJf
tile

output
shaft
thai
is

they
operate
at

a

speed
in

proportion
10

the
vehicle

speed
The
line

press
retis

applied
to

those
valves

s
the

input
from
the

control

valve

through
the

transmission

case
rear

flange
and
oil
distributor

The

governor

pressure
in

proportion

to
the

ouiput
shaft

speed
vehicle

speed
is

led
to
the
shift
valve
ofthe

control
valve

through
the

opposite

route
of
the

output
In

this
manner

speed
change
and
line

pressure
are

controlled

Operation
of

secondary

governor
valve

T
e

secon

ary
valve

is
a

contro

valve

Y
hich
receives

line

pressure

an

cqQ
rols
the

governor

pressu
e

When
the
manual

valve
is
selected

at
D
2

or
l

range
line

pressure

is

applied
t
the
ri

g
sh

aped
area
of

this
valve
from
circuit
I

l
and
this

I

v

Jy
is

depressed
lOW
jr
tI
c

fer

Movemcnt

of
this
valvl
III
a
cr

in

positillll
doses
the
dr
uit

from

Olto

15
while

simultaneously

making
a

sr
rronl
IS
to
Iii
center

d
niin

port
and

press
re

in
tllc
ci
rJ

it

l5j
is

lowered

When

thc
vehicle
is

stopped
1
d

the

cenlrifugal
force
of
this
valve
is
zero

the
v
lve

is
balanced
At
this

poini
a

govcr
lOr

pressurc
y
hich

bal
i1
nced

with

th

spr
ng
force

occurs
on
IS

Wh
n

thc
vehicle
is

st
rted
nd

the

centrifugal

fqr
incre

ses
this
valve

movcs

slightly
10

Ihc
oUlSide
and

as

the

space
from
I

to
IS
increases

space
from
15
to
the

drain

port

simultaneously
decreases
As
a

resull

governor
pressure
of

15
increases

and
the

governor
pressure
is
balanced

with
the
sum
of

centrifugal
force
and

spring
force
The
governor

pressure

thus
changes
in

response
to
the
vehicle

speed
change
centrifugal
force

Operation
of

prlmar

governor
valve

The
valve
is

an
ON
OFF

valve

which
closes
the

governor

pressure

IS

regulated
by
the

secondary

gover

nor
valve
when
the
vehicle
reaches
the

minimum

speed
and
when
the
vehicle

speed
exceeds
a
certain

level
the

governor
opens
and
forwards

the

gov

ernor

pressure
15
to
the
control

valve

When
the
vehicle
is

stopped
the

governor

pressure
is
zero
However

when
the

vehicle
is

running
slowly

this
valve

is

depressed
to
Ihe

center

and
the

groove
to
15
is
closed
since

the

governor
pressure
applied
to
the

ring

shaped
area
is

higher
than
the

centrifugal
force
of
this
valve
When

the

governor
speed
exceeds
a
certain

revolution
the

governor
pressure
in

the
circuit
15
also
increases
How

ever
as
the

centrifugal
force

increases

and
exceeds
the

governor
pressure
this

valve
moves
toward
the
outside
and

the

governor
pressure
is

transmitted
to

the
circuil
5

Two
different
valves
are

employed

in

the

governor
so
that
it
will
inde

pendently
control
the

speed
at

high

and
low

speeds
That
is
within
the
low

speed

range
the

governor

pressure
is

not

generated
because
of
the

primary

valve
whereas
at
the

high
speed
range

above
the

breaking
point

governor

pressure
is

regulated
by
the

secondary

valve

The

breaking
point
is
the

point
at

which

the
function
of

one
of
the

governor
is
transferred
to

the
other

as
the

speed
changes
from
the

low

speed
to
the

high

speed
range
Automatic
Transmission

To
onlml

valve

l
Governor

pre
S1I
1I5
j

I

Q
J
J

f
1

1

CID

l

l
m

Line

pressure
t
D@

I

Primary
governor

2
Secondary

governor

3
Governor
valve

body
AT090

4

Oil
di
lributor

5

Output
sh
lft

Fig
AT
7
Cr05s
sectionallliew

of

governor

CONTROL

VALVE
ASSEMBLY
Ai09

Fig
AT

S

Output
shaft
with

oil

distributor
and

overnor

r

@

@
0

aBUlllI8

iUQlli
V

JlAU

I
Oil
distributor

2
Governor
nlve

body
A

T092

3

Primary
governor

valve

4

Secondary
governol

valve

Fig
A
T

9

Exploded
view

of
governor

Flow

cbar
of

control
valve

system

Oil
from

pump

Regulator
valve

1

I
i

j

Throttle
valve

I
I
l

Manual
valve
I

I

I

I

I

I

I

L

n
L

j
Speed
change

valve
I

I

t

t

I

I

I

I

I

I
Governor
I

I
valve

I

I

I

L
L

1
II
Auxiliary
valve

Line

pressure

j
Clutch
and
brake

The
control
valve

assembly
receives

oil
from
the

pump
and
individual

signals
from
the
vacuum

diaphragm

and
transmits
the
individual

line

pres

sures
to
the

transmission
friction
ele

ment

torque
converter
circuit
and

lubricating
system
circuit
as

outputs

More

specifically
the
oil
from
the
oil

pump
is

regulated
by
the

regulator

valve
as
line

pressure
build

up
the
line

pressure
is

fed
out
from

the
control

valve

assembly
through
various

direc

AT
6
tion

changeover
valves

including
ON

OFF
valve
and

regulator
valves
are

newly
reformed
to
a
throllle

system

oil

pressure
and

operate
other
valves

Finally
the
line

pressure
is

transmilled

to

the

required
dutch
or

brake
servo

pisJon
unit
in

response
to
the
individu

af

running
conditions
after
re

ejving

signals
from
the

va
uum

diaphragm

downshift
solenoid

governor
V
dlvc

and
or
manual

linkage

The
control
valve

assembly
consists

of

the

following
valves
See

Figure

AT

20

I
Pressure

regulator
valve

PRV

2

Manual
valve

MNV

3
I

st
2nd

shift
valve

FSV

4

2nd
3rd

shift
valve

SSV

5

Pressure
modifier
valve

PMV

6
Vacuum
throttle
valve

VTV

7

Throttle
back

up
valve

TBV

8
Solenoid
downshift
valve
SDV

9

Second
lock
valve
SL
V

10
2nd
3rd

timing
valve

TMV

Pressure

regulator
valve

PRV

The

pressure
regulator
valve
re

ceives
valve

spring
force
force
from

the

plug
created

by
the
throttle

pres

sure
16
and
line

pressure
7

and

force
of
the
throttle

pressure

18

With
the
interaction

of
those
forces

the
PRY

regulates
the

line

pressure
7

to
that

most
suitable
for
individual

driving
conditions

The
oil
from
the
oil

pump
is

ap

plied
to

the

ring

shaped
area

through

orifice
20
As

a
result
the
PRV
is

depressed
downward
and
moves
from

port
7

up
to
such
extent
that
the

space
to
the
next
drain

port
marked

with
X
in

Figure
AT
10

opens

slightly
Thus
the

line

pressure
7
is

balanced
with
the

spring
force
there

by
balancing
the
PRV
In
this

opera

tion
Ihe

space
from

port
7
to
the

subsequent
converter
oil

pressure
14

circuit
has
also
been

opened
As
a

result
the
converter
is
filled

with

pressurized
oil
in
circuit
14
and
this

oil
is
further
used
for
lubrication
of

the
rear
unit
Moreover

part
of
the
oil

is
branched
and
used
for
lubrication

of

the
front
unit
for
the
front
and
rear

clutches

When
Ihe
accelerator

pedal
is
de

presscd
the
throttle

pressure
16
in

creases
as
described
in
the

preceding

paragraph
oil

pressure
is

applied
to

the

plug
through
orifice
21

and
this

pressure
is

added
to
the

spring
force

As

a
result
the
PRV
is

contrarily

forced

upward
space
to

the
drain

port

is
reduced
and
Ihe

line

pressure
7

increases
Automatic

Transmission

11

AT095

Fig
AT
10
Pressure

regulator
ualue

When

the

range
is
selected
at
R

Reverse

the
line

pressure
6
is

applied
10

the

plug
in
a
manner
identi

caito
the

throttle

pressure
16
and

is

added
10
the

spring
force

Consequent

ly
the
line

pressure
7

further
in

creases

When
vehicle

speed
increases

and

the

governor
pressure
rises
the

theot

tle

pressure
18
is

applied
to
the

port

on
the

top
of
the
PRV

and

pressure
is

applied
contrarily
against
the

spring

force
As
a

result
the
line

pressure
7

decreases
Moreover
at
individual

con

ditions
the
line

pressure
7

is

equal
to
the
line

pressure
6

and
the
throttle

pressure
16
is

equal
to
18

Manual
valve
MNV

The
manual
lever

turning
motion
is

converted
to

reciprocating
motion

of

the
manual
valve

through
a

pin
and

the
MNV
is

positioned
so
that
the
line

pressure
7
is
distributed
to
the

indi

vidual
line

pressure
circuits
at
each

P

R
N

D
2
or
I

range

as

shown
below

P

range

7
4
SDV
and
TBV

5

FSV
12
TBV
and

Low

reverse
brake

R

range

7
4

same
as
above

5

same
as
above

6

PRY
and

SSV
F
C

and
band
release

N

range

D

range

7
7

None

I

Governor
valve

FSV

and
rear
clutch

2

SLY

3

SL
V

and
SSV

2

range

7
I
Same
as
above

2

SL
V
9
Band

applied

4
SDV
and
TBV

I

range

7
I
Same
as
above

4
Same

as
above

5

FSV

Moreover
1

2
3
4
5

and

6

are

always
drained
at
a

position

where
the
line

pressure
is

not
dis

tributed
from
7

u
JJX
g4Vhl

dIillillt
1
dlMIi
W
ld

IiIb
It
i
B
J

jd
l
tJj
fitMi
td

j
L@

x
x

j
j

P
R
N

17
l

AT7
AT096

Fig
AT
11

Manual
ualvp

1st

2nd
shift

valve
FSV

The

FSV
is
a

transfer
valve
which

shifts

gears
from

low
to

second
When

Ihe
vehicle
is

stopped
the

FSV
is

depressed
to

the

right
side

by
force
of

a

spring
located
on
the

left
side

putting
the

FSV
is
in
the

low

position

When
vehicle

speed
increases
the

governor

pressure
15
is

applied
to

Ihe

right
side
of

the
FSV
and
the
FSV

is
forced

toward
the
left

Contrarily

the
line

pressure
I

togelher
with
the

spring
force
force

the
FSV

toward
the

right

opposing
the

governor

pressure

15

When
the

vehide

speed
exceeds
a

certain
level

the

governor
pressure

15
exceeds
the
sum
of
the

throttle

pressure
and
Ihe

spring
force
and
the

FSV
is

forced
toward
the
left

When
the
FSV
is

depressed
10
a

certain

position
the

lire
pressure
I

is

closed
and

only
the

spring

depresses

the

FSV
toward
the

right
and
it
is

depressed
to

the
end
for

a
moment
As

a

resull
the

line

p
ressure

lJ
is
for

warded

to
8
the
band

servo
is

engaged

through
the
SLY

and
the

speed
is
shifted
to
2nd

With
the

accelerator

pedal

depressed
the
FSV

remains
iIi

the
Low

position
unless

the

governor
pressure
IS
increases

to

a

high
leVel

corresponding
to
the
line

pressure
I
since

the

line
pressure

I

increase
when
the
accelerator

pedal
is

depresse9

Contrarily
when

vehicle

speed
de

creases

the

governor

pressure
15

decrease
Howeve
f

the

gear
is
not

shifted
to

Low

nless
the

governor

pressure
15
becomes

zero
since

the

force

depressing
the
FSV
toward
the

right
is

being
delivered

only
by
the

spring

Low
in

range
I
is
led
to

the

low
and
reverse

clutch
from
line

pres

sure
5

through
line

prbssure
12

2nd
is
simultaneousi

y
led
to

the
ieft

end

spring
unit

Consequently
al

thougp
the

goverflor
pressure
in

creases

the
valve
is
still
forced
toward

the

right
and
the
SFV
is

fixedjn
the

Low

position
When
kicked
down
to

the
2nd

speed
the
SDV

operates

and

the
line

pressure
13
forces
the

FSV

toward
the

right
Although
the
Automatic
Transmission

governor
pressure
15
is

considerably

high
the
valve
is

forced

completely

toward

the

right
and
the

FSV
is

returned
to
the

Low

position
This

operation
is

alled

Kickdown
shift

15

j

13

1

c5

I

0

t

r

I

I

q
1

AT091

Fig
AT
12

lsl
2nd

shift
valve

2nd
3rd

shift
valve
SSV

The

SSV
is

a
transfer
valve

which

shifts

gears
from

2nd
to

3rd

When
the
vehicle
is

stopped
the
SSV

is

forced
toward

the

right
by
the

spring
and
is
in
the

2nd

position
It

is

so

design
d
however

that
the
FSV

can

decide
to
shift

either
to

Low
or

2nd

When

the
vehicle

is

running
the

governor
pressure
15
is

applied
to

the
right
end
surface

and
th
SSV
is

forced

toward
the
left

Contrarily
the

Spri
l
force

line

pressure
3

and

throttle

press
re
19
force
the

SSV

toward
the

right

When
vehicle

speed
exceeds
a
cee

tain

level
the

governor

pressure
sur

passes
the
sum
of
the

spring
force
line

pressure
and
throttle

pressure
and
the

valve
is
forced
toward

the
left
The

line

pressure
3
is

then
closed
Con

sequently
the
forces

being
rapjdly

unbalanced
the
force

depressing
the

SSV
toward
the

right
decreases
and

thus
the
SSV
is

depressed
to

the
l

ft

end
for
a
moment

With
Ihe

SSV

depressed
toward
the

left
end
lhe

line

pressure
3

is
connected
with

the
line

pressure
10

the
band
servo
is
re

leased
the
front

clutch
is

engaged
and

AT
8
speed
is
shifted
to

3rd

When
the

accelerator

pedJI
is

de

prcssed
both
the

line

pressure
3
and

the

throttle

pressure
19

are

high
allll

the

SSV
is
thus

retained
in
nd

unless
the

governor

pressure
15

ex

ceeds
the

line

pressure
3
and

the

throttle

pressure
19

In
the

3rd

position
force

de

pressing
ihe
SSV

toward
the

right
is

retained

only

by
the

throttle

pressure

16
and

the
throttle

pressure
16

is

slightly
Idwer

than
that
toward
the

right
which
is

applied
while

shifting

from
2nd
to

3rd

Consequently
the

SSV
is
returned

to
the

2nd

position
at
a

slightly

lower

speed

Shifting
from
3rd
to

2nd

occurs
at
a

speed
slightly
lower

than
that

for
2nd
to
3rd

shifting

When
kicked
down
at
3rd

line

pressure
13
is

led
from
the
SDV
and

the

SSV
is
forced

toward
the

right

Although
the

governor
pres
ure
is

con

siderably
high
the
valve
is
forced

completely
loward
the

right
and
tht

SSV
is

thus
returned
to
2nd

posi

tion

fhis

operation
is
called
K
cli

down
shift

When

the
shift
iever
is

shifted
to

2

or
I

range
at
the
3rd

speed

the
line

pressure
3
if
diained

at
the

MNV

Consequently
the

front
clutch

and
band
servo

releasing
oils

are

drained
As
a
result

the
transmission
is

shifted
to
2nd
or
low

speed
ai

though
the

SSV
is
in

the
3rd

posi

tion

When
the

specd
IS

shifted
io

the

3r
1
a
one

way
orifice
24

on
the

topof
the
SSV
relieves
oil

transmitting

velocity
from
the
line

pressure
3
to

the
line

pressure
10
and
reduces

the

shock

generated
fioni

the

shifting

Contrarily
when
the
lever
is
shifted

to
2
or
I

range
and
the

speed
is

shifted
from
3rd
to
the
2nd
the

orifice

checking
valve

spring
24
is

depressed
the
throttle

becomes
in

effective

the
line

pressure

10
is

drained

quickly
and

delay
in

shifting

speeds
is

thus
eliminated

The
throttle
of
line

pressure
6

transmits
Hie

oil

transmitting

velocity

from
line

pressure
6
to
line

pressurc

10
wtien
the

lever
is
shifted
to
the

R

range
and
transmits
drain
veloci

ty
from
line

pressure
10
to
line

3

Jit
f
ng
valve

24

1

3

L
l

r

I
Js

I
i

ilr
t
pressure
6
when

shif
ing
from
3rd

to
2nd
at
D

range
Thus
the

throttle
of
line

pressure
6
reduces

the

shock

generated

fro
shifting

A

plug
in
the

SSV
left

end

readjust

the

throttle

piessu
e
I
6
which
varies

depending
on
the

engine
throttle
con

dition
to
a
throttle
pressure
19

suiled
to
the

sp
ed

change
control

Moreover
the

plug
is
a
valve
which

applies
line

P

esspre
13
in
lieu
of
the

throttle

pressure
to
the
SSV
and
the

FSV
when
kickdowri
is

performed

When
the
throttle

pressure
16
is

applied
to
the

left
side
of
this

plug

and
the

plug
is

epressed
toward
the

right
a

slight

space
is
formed
from
the

throttle

pressure
6
10

19
A

throt

tIepressu
19

w
1iFh
is
lower

by
the

pressure
loss

equivalent
to
this

space
is

rH

1

Pressure
Odifier
valve
PMV

I

Compared
to
the

operating

pressure

required
in

starting
th
vehicle
the

ppwer
trimsinitting
capacity
of
the

clutch
that
is

required
operating

pres

sure

may
be

lower
when
the
vehicle
is

once
started
When
the
line

pressure
is

retained
at

a

high
level

up
to

a

high

vehicle

speed
shock

gerieraled
from

the

shirring
increases
arid
the

oil

pump
loss
also
jncrdases
In
order
to

prevent
his
the
t

lrott
le

pressure
must

be
l

hanged
over

with
the

operation
of

the

governor
pressure
15
to
reduce

Ihe
line

pressure
The
PMV
is
used
for

this

purposc
Automatic

Transmission

generated
the

piessure
loss
is
adde
d
to

the

spring
force

and
the

plug
is
lhus

forced

back
from
the

right
to
the

left

When
this

pressure
19
increases
ex

cessively
the

plug
is
further

depressed

toward
the

left

space
from
the
lhrot

tle

pressure
19
to

the
drain
circuit

13

increases
and
the
throttle

press

ure

19
decreases
Thus
the

plug
is

balanced
imd
the
throttle

pressure

19
is

reduced
to
Ii
certain
value

against
the
throttle

pressure
6

Wheri

performing
kickdowri

the

SDV
moves
a

high
line

pressure
is

led

to
the
circuit

19
from
the
line

pressure
circuit

13
which
had

been

drained

the

plug
is
forced
toward
the

left

and
circuit

19
becomes

equal
to

the
line

pressure
13

I

W
15

I

A
TOgS

Fig
iT
13
2nd
3rd

shift
vallJe

I

When

the

governor
pressuie
IS

which
is

applied
to
the

right
side
of

the
PMV
is
low
the
valve
is
forced

toward

the

right
by
the
throttle

ines

sure
16

applied
to
the
area
differ

ence
of
the
value
and
the

spring
foice

and
t

he
circuit

from
circuit

16
to

circuit
18
is
closed
However
when

vehicle

speed
increases
andl
the

gaver

nor

pressure
15
exceeds
a
certain

level
the

governor
pressure
toward

the

left
which
is

applied
to
the

right
side

exceeds
the

spring
force
and
the

throt

tle

pressure
16

toward
thc

right
the

valve
is

depressed
loward
the
lefi

and

the
throttle

pressure
is
led
from
circuit

AT

9
16
to
circuit

18
This
throttle

pressure
18
is

applied
to
the

top
of

the
PRV
and
the
force
of
the

line

pressure
source
7
is
reduced

Contra

rily
when

the
vehicle

speed
decreases

arid
the

governor

ipressure
15
de

creases
the

force
toward
the

fight

exceeds
ithe

governor
pressure
the

valve
is

forced
back
toward
the

right

and
the

throttle

pressure
18
is

drained
to
the

spring
unit

This
valve
is

sWitched
when
the

throttle

pressure
and
the

governor

pressure
are

high
or
when

tIiey
are

both
Tow
i

i
I
11

18
16

n

r

I

I

15

AT099

Fig
AT
14

Pre
ure

modifier
valve

Vacuum
thro
le
valve
VTV

The

vacuum
t
rottle
valve
is
a

regula
tor
valve

whiCh
uses
the
line

pressure
7

for
the

pressure
source

and

regulates
the

throttle

pressure
16

I

which
is

proportioned
t
the

force
of

the

vacuum

diaphragm
The
vacuum

dia

phragm
yories
depending
on
the

engine
throt
le

condition

negative

pressure
in
the

inta
e
line

When
the
line

pressure
7
is

ap

plied
to
the
bottom

through
the

valve

hole
and
the
v

a
ve
is

forced

upward

space
from
the
line

pressure
7
to
the

throttle

pressure
16
is
dosed
and

the

space
from
the
Ihrottle

pressure

16
to

the
drain
circuit
17
is
about

to

open
In

this

operation
the
throttle

pressure
16
becomes
lower
than

the

linep
s

ureY
btthe
p
e
sur

9
iv

alenl
of
the

loss
of

space
and
Ihe

force

depressing
tlie
rod
if
the

vaeuum

diaphragm
is

balanced
wit

Ii
thethrot

tie

pressure
16
a

pplied
upward
tOlthe

bottom

When
the

erigine

torque
is

high
Ihe

negative
pressure
in
the
intake
iirie

rises

tending
ioward

atmospheric

pressure
and
the
force
of
the
rod
to

depress
the
valve
increases
As
a
result

the
valve
is

depressed
downward
the

space
from
the
throttle

pressure
16

to

the
drain

17
decreases

and
the

space
from
the
line

pressure
7
to

Ihe

throttle

pressure
16
increases

Consequently
the
throttle

pressure

16
increases

and
the

valve
is

bal

anced

Contrarily
when
the

engine

torque
lowers
and
the

negative
pr

sure
in

the
intake
line

lowers

tending

toward
vacuum
the
force
of
the

rod

depressing
the
valve
decreases

and
the

throttle

pressure
16
also
decreases

When

pressure
regulated

by
the
throt

tle

back
p
valve
described
in
the

subsequent
paragraph
is
led
to
circuit

17
a

high
pressure
is

applied
through

the

space
from

the
circuit
17
to
the

throttle

pressure

16
Consequently

the
VTV
is
unbalanced
the

throttle

pressure
16
becomes

equal
to
the

back

up
pressure
17
and
the

valve
is

locked

upward

I

16

III
AT100

Fig
AT
15

Vacuum

throttle
valIN

Throttle

back

up
valve

TBY

Usually
this

valve
is

depressed

downward

by
the

spring
force

and

circuit

17
is

drained

upward

As

soon
as
the
lever
is

shifted
either

to
2

or
I

range
line

pressure
is

led
from

circuit
4

the
line

pressure
is

applied
to
the
area
difference

of
the

valve
the

valve
is
forced

upward
the

space
from

circuit
4
to
circuit

17
is

closed

and
with
the

space
from
circuit
Automatic
Transmission

17
to
Ihe

upper
drain
about
to

open

the
back

up
pressure
17
which
is

lower
than
the

line

pressure
4

by
the

pressure
loss
due
to
the

space
from

circuit
4
to

circuit

17
is
balanced

with

the

spring
force

Further
when

gear
is

shifted
from

2nd

to
Low

at
the

range
I
line

pressure
is

led
from
circuit

12
and

the
line

pressure
is

applied

pward
to

the
bottom
of
the

valve

through
the

valve
hole

Consequently
the
valve
is

forced

upward
and
locked
As
a

result
the

space
from
the
line

pressure

4
to

the
back

up
pressure
17
is

closed

completely
and
the
back

up

pressure
17
is

drained

upward

AT101

Fig
AT

16
Throttle
back

up
lJ
Jlve

Solenoid

downshift
valve

SDY

This
valve

is
a
transfer
valve
which

leads
the
line

pressure
7

to
13

and

transmits
the
same
to
the
FSV
and

SSV
when
a
kickdown

signal
is
re

ceived
from

the
downshift
solenoid

Usually
the
solenoid

push
rod
and

valve
are
locked

upward
by
the

spring

in
the
lower
end
and
the
circuit
from

line

pressure
4
to
line

pressure
13
is

opened

When
kickdown
is

performed
the

push
rod

operates
Ihe
valve
is
de

pressed
downward
and
the

circuit

from
line

pressure
7
to

line

pressure

13

opens
Line

pressure
13

opposes

the

governor
pressure
15
at

Ihe
SSV

and
FSV
thus

accomplishing
the

downshift

operation

AT
10
r

AT102

Fig
AT
17

Solenoid

dow
hift
valve

Second

lock

valve
SLY

This
valve
is
a
transfer

valve
which

assists
the
shift

valve
in

determining

the
fixed

2nd

speed
at

the
2

range

In

the
D

range
the

sum
of
the

spring
force

and
line

pressure
3

APplied

upward
xce
ds
the

linepres

sure
2
which
is

applied
to

the
valve

area
difference

as
a
downward
force

As
a
result

the
valve
is

locked

upward

and
the
circuit
from
line

pressure
8

to
line

pressure
9
is

opened

Consequently
the
FSV

becomes

the
2nd

speed
condition
and
line

pressure
is

led
to

the
band

servo

engaging
circuit
9

only
when
line

pressure

1
is
released

to
line

pressure

8

In
the
2

range
the

upward
force

is

retained

only
on
the

spring
and
the

downward
line

pressure
2

exceeds

the

upward
force

As
a
result
Ihe
valve
is

locked

downward
line

pressure
2
is

released

to

9

regardless
of
the

operating

condition
of
the
FSV
and
the

band

servo

is

engaged

J

2

8

ATl03

3

Fig
AT
18
Second
lock
lJ
Jlve

Automatic
Transmission

d

n
ern

I

lLU
I
J

A1
094

1

Pressure

regulating
valve
PRV

2
Manual

val
MNV

31st
2nd
shift

val
fSV

4

2nd
3rd
shift

val
SSV

5

Pressure
modifier
valve
PMV
6
Vacuum
throttle
valve
VfV

7

Throttle
back

up
valve
TBV

8
Solenoid
down

shift
valve
SDV

9
Second
lock
valve
SL
V

10
2
3

timing
val
TMV

Fig
AT
20
Controloolve

AT
12