1973 DATSUN B110 clutch

The
model
3N71
B

automatic
trans

mission
is
a

fully
automatic
unit
con

sisting

primarily
of
element

hydrau

lic

torque
converter
and
two

planetary

gear
sets
Two

multiple
disc

clutches
a

muItiple
disc
brake
a
band
brake
and

a

one

way
sprag
clutch

provide
the

friction
elements

required
to

obtain

the

desired
function
of
the
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
Vehicle

speed

and

engine
manifold
vacuum

signals

are

constantly
fed
to
the
transmission

to

provide
the

proper
gear
ratio

for

maximum

efficieq
cy
and

performance

at
all

thrqttIe
openings

The

iMiij
l

3N7I
B
has

six
selector

position
f

P
R
N
D

2
1

k
Park

position
positively
locks

the

c
ut

put
shaft
to
the
transmission

case

RY
means
of
a

locking
pawl
to

prev
nt
the
vehicle

from

rolling
either

direction

This

position
should
be
selected
when

ever
the

driver
leaves
the

vehicle

The

engine
may
be
started
in
Park

pQlition

OR
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
CHASSIS

DESCRIPTION

D
Drive

range
is
used
for

all

normal

driving
conditions

Drive

range
has

three

gear
ratios
frum

the

starting
ratio

to
direct
drive

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

range
can
be

selected
at

any
vehicle

speed
and
the
transmission

will

shift
to
second

gear
and

remain
in

second
until

vehide

speed
is

reduced

to

approximately
40
to
50

kmfh
25

to
31

MPH

I

range

position
prevents
the

transmission
from

shifting
out
of
low

gear
This
is

particularly
beneficial

for

maintaining
maximum

engine
braking

when
continuous

low

gear

operation
is

desirable

The

torque
converter

assembly
is

of

welded
construction
and
can
not
be

disassemble
for
service

Fluid
recommendation

Use

having

only
in

mission
automatic

transmission
fluid

DEXRON
identifications

the
3N7I

B
automatic
trans

AT
2
IA
e

l
csr
4o

J

r
s

Identification
number

Stamped
position

The

plate
attached
to

the

right

hand

side
of
transmission
case
as

shown
in

Figure
AT
I

ii

II

r

4
1
r

I

to
i

AT057

Fig
AT
1

Identification
number

Identification
of
number

arrangements

See
below

Model
code

JAPAN

AUTOMATIC

Z
TRANSMISSION
CO
LTD

I
MODEL

XOIOO

J
I
NO
2412345

Unit
number

Number

designation

2
4
2
3
4

5

L

Seriat

production

number

for
the

month

Month
of

production

X
Oct
Y
Nov
Z

Dec

Last

figure
denoting

the

year
A
D

r

AUTOMATIC
TRANSMISSION

1

1

1

I
L
@
CD

@
@

ID
@
@

h
r

H

@
@
@
@
@
@
@
4
@
@

t

I

fA

TIl70

4
t
ill

pJrP

I

Transmission
ase

II
Governor
Tightening
torque
T
of

@T
0
5

to
0
7

2

Oil
pump
12

Output
shaft
bolts
and
nuts

kg
rn
ft
Ib
3
6

to
5
1

3
Front
clutch

13
Rear
xtcnsion

@T
0
8

to
1
0

@T
2
0

to
2
5

4
Band
brake
14

Oil

pan

@T
5
8
to
7
2
14
to
18

5
Rear
clutch
15
Control

valve
4
to
5

@T
1
3
to
1

8

6
Front

planetary
gt
ar

16

Input
shaft

@T
29

to
36
9
4
to

13

7
Rear

planetary
gear
17

Torque
converter
6
5
to
7
5

@T
0
55
to
0
75

8
One

way
clutch
18

Converter

housing

@T
47

to
54
4
0
to
5
4

9
Low
Reverse
brake
19
Drive

plate
0
6
h

Q
8

Q
T

0
25
to
0
35

10
Oil
distributor
4
3
to

5
8
1

9
to
2
5

Fig
AT
2
Cross
sectional
uiew

of
3N71
B
automatic
transmission

I

AT
3

l

t

CHASSIS

HYDRAULIC
CONTROL
SYSTEM

l
FUNCTIONS
OF
HYDRAULIC

CONTROL

UNIT

AND
VALVES

Oil

pump

Manual

linkage

Vacuum

diaphragm

Downshift
solenoid

Governor
valve

Control

valve

assembly

HYDRAULIC
SYSTEM
AND

MECHANICAL
OPERATION
CONTENTS

P

range
Park

R

range
Reverse

N

range
Neutral

D

range
Low

gear

D2
range
2nd

gear

D3
range
Top
gear

D

range
kick
down

2

range
2nd

gear

1
range
Low

gear

12
range
2nd

gear
AT
4

AT
4

AT
5

AT
5

AT
5

AT
5

AT

7

AT13
AT
14

AT
16

AT
18

AT
20

AT
22

AT
24

AT

26

AT
28

AT
30

AT
32

FUNCTIONS
OF

HYDRAULIC

CONTROL
UNIT

AND
VALVES

The

hydraulic
control

system
con

lain
a
oil

pump
for

packing
up
oil

from
the
oil

pan
through
the
oil

strainer
A

shift
control

is

provided
by

two

centrifugally
operated
hydraulic

Oil

pump

Manual

linkage

Vacuum

diaphragm

Downshift

solenoid

Governor
valve

Oil

pump

The
oil

pump
is
the

source
of

control
medium
in
other
words
oil

for
the
control

system

The
oil

pump
is
of

an
internal

involute

gear
type
The
drive
sleeve
is
a

part
of
the

torque
converter

pump
governors
on
the

output
shaft
vacuum

control

diaphragm
and
downshift

solenoid

These

parts
work

in

conjunc

tion

with
valves
in

the
valve

body

I

I
Control
valve

impeller
and
serves
to
drive

the

pump

inner

gear
with
the

drive
sleeve

direct

ly
coupled
with
the

engine
operation

The
oil
flows

through
the

following

route

Oil

pan
Oil
strainer
bottom

of
the

control

valve
Control
valve
lower

AT
4
assembly
located
in
the
base
of
the

transmission
The
valves

regulate
oil

pressure
and

direct
it

to

appropriate

transmission

components

I
Torque
converter

Front
clutch

Rear
clutch

Low

and
reverse

brake

Band
brake

Lubrication

body
suction

port
Transmission
case

suction

port
Pump
housing
suction

port

Pump
gear
space
Pump

housing
delivery

port
Transmission

case

delivery
port
Lower

body

delivery
port
Control
valve
line

pressure
circuit

Control

valve

assembly
AUTOMATIC
TRANSMISSION

Oil

from

pump

ru
nn

i

I
I
I
Throttle
valve

I

I

1
m
nn

I
Auxiliary
valve

I
Regulator
valve

j

Manual
valve

I

Uoe

pressure

Speed
change
L

I
Governor

valve

I
I
valve

J
1
1

Clutch
and
brake

Flow

chart
of

control
valve

system

The
control
valve

assembly
receives

oil

from
the

pump
and
the

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
the
out

puts
To
be

more

specifically
the
oil

from
the
oil

pump
is

regulated
by
the

regulator
valve
and
line

pressures
build

up
The
line

pressures
are
fed
out
from

the
control
valve

assembly
as

they
are

through
various
direction

changeover

valves

including
ON
OFF
valve
and

regulator
valves

newly
reformed
to
a

throttle

system
oil

pressure
and

op

crates
other
valves

or

finally
the
line

pressure
are
transmitted
to

the
re

quired
clutch
or
brake
servo

piston

unit
in

response
to
the

individual

running
conditions
after

receiving
sig

nals
from
the

previously
described

vacuum
diaphragm
downshift
sole

noid

governor
valve

and
or

manual

linkage

The
control
valve

assembly
consists

of
the

following
valves

Pressure

regulator
valve

2
Manual
valve

3
1st

2nd
shift
valve
4

2nd
3rd
shift

valve

S

Pressure

modifier
valve

6

Yacuum
throttle
valve

7

Throttle
back

up
valve

8
Solenoid

downshift
valve

9
Second

lock
valve

0

2nd
3rd

timing
valve

Pressure

regulator
valve

PRV

The

pressure
regulator
valve

re

ceives

valve

spring
force
force
from

plug
created

by
the
throttle

pressure

16
and
line

pressure
7
and
force

of

the

throttle

pressure
18

With
the

mutual

operations
of
those
forces
the

PRY

regulates
the
line

pressure
7
to

the

most
suitable

pressures
at
the

individual

driving
conditions

The
oil
from
the
oil

pump
is

ap

plied
to
the

ring
shaped
area

through

orifice
20
As

the
result
the
PRY
is

depressed
downward
and

moves
from

port
7

up
to
such
extent
that
the

space
to
the

subsequent
drain

port

marked
with
x
in

Figure
AT
10

opens
slightly
Thus
the
line

pressure

7
is
balanced
with
the

spring
force

AT
7
and
the
PRY
is

thereby
balanced
In

this
the

space
from
the

port
7

to
the

subsequent
converter
oil

pressure
14

circuit

has
also
been

opened
As

the

result
the

converter
is
filled
with
the

pressurized
oil
in
the
circuit
14
and

the

oil
is

further
u
d

for
the

Iubrica

tion
of
the
rear
unit
Moreover

a

part

of
the
oil
is

branched
and

used
for
the

lubrication
of
front
unit

for
the
front

and
rear
clutches

When
the

accelerator

pedal
is
de

pressed
the
throttle

pressure
16
in

creases
as

described
in
the

preceding

paragraph
oil

pressure
is

applied
to

the

plug
through
orifice
21
and
the

pressure
is

added
to
the

spring
force

As
the

result
the
PRY
is

contrarily

depressed
upward
space
to
the
drain

port
is

reduced
and
the
line

pressure

7
increases

Afl

II

Jwi
06

A

J
L
I

7

I

tf

Iij

BL

i
il
J

jti
r

x

r
1
J

I

l

I

X

6

C

l
o

ii
J

f

A

T09S

Fig
AT
10
Pressure

regulator
value

tr
r

When
the

range
is

selected
at
R

Reverse

the
line

pressure
6
is

applied
to

the

plug
in
the

manner

identical
to

the
throttle

pressure
16

and
is

added
to

the

spring
force

Consequently
the

line

pressure
7

further
increases

When
the
vehicle

speed
increases

and
the

governor
pressure
rises
the

throttle

presSure
18
is

applied
to
the

port
on
the

top
of
the

PRY
and

pressure
is

applied

contrarily
against

the

spring
force
As

the
result
the
line

pressure
7

lowers

Moreover
at

the

individual
conditions

the
line

pressure

7
is

equal
to

the
line

pressure
6
and

the
throttle

pressure
16
is

e
qual
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

properly

positioned
so

that
the

line

pressure
7
is

distributed

to
the
individual
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
7

None

D

range

7
1

Governor
valve

FSV

and
rear
clutch

2
SLY

3
SLY
and
SSV

2

range

7

1
Same
as
above

2
SL
V

9
Band

applied

4

SDV
and
TBV
CHASSIS

I

range

7

reI
Same
as
above

4
Same

as
above

5

FSV
Moreover

I
2
3
4

5
and

6
are

always
drained
at
a

position

where

the
line

pressure
is
not
dis

tributed
from
7

xJ2

U
I
V

Jl

ft
g
f

P
R
NeD
2
1

3nl

lst

2nd
shift
valve
FSV

The
FSV
is
a

transfer
valve

which

shifts

speed
from
low
to
second
When

the
vehicle
is

stopped
the

FSV
is

depressed
to
the

right
side

by
the
force

of
a

spring
located
in

the
left
side
and

thus
the
FSV
is
in
the

Low

posi

tion

When
the

vehicle

speed
increases

the

governor

pressure
IS
is

applied

to
the

right
side
of

the
FSV
and
the

FSV
is

depressed
toward

the
left

Contrarily
the
line

pressure
I

and

throttle

pressure
19

depress
the
FSV

toward
the

right
together
with

the

spring
force

and
thus

oppose
to
the

governor
pressure
IS

When
the
vehicle

speed
exceeds
a

certain

level
the

governor
pressure

15
exceeds
the

sum
of

the
throttle

pressure
and
the

spring
force
and
the

FSV
is

depressed
toward

the
left

When
the
I
SV
is

depressed
and

reaches
a
certain

position
the
line

pressure
1
and
the
throttle

pressure
fl

4V6
I

I

l
t
I

1

f

7V
5

AT096

Fig
A
T

II
Manual
ualve

19
are
closed

only
the

spring
de

presses
the
FSV
toward
the

right
and

the
FSV
is

depressed
to
the
end
for
a

moment
As

the
result
the
line

pres

sure

I
is
forwarded

to
8
the
band

servo
is

engaged

through
the

SL
V

and

thus
the

speed
is

shifted
to
2nd

With
the

accelerator

pedal

depressed

the

FSV
is

remained
in

the
Low

position
unless
the

governor
pressure

IS
increases
to
a

high
level
cone

sponding
to

the
line

pressure

I
and

the
throttle

pressure
19
since

the
line

pressure
I

and
the
throt
tIe

pressure

19
increase

when
the

accelerator

pedal
is

depressed

Contrarily
when
the
vehicle

speed

lowers
the

governor

pressure
IS

reduces
However
the

speed
is

not

shifted
to
Low

unless
the

governor

pressure
15
becomes
zero
since

the

force
to

depress
the
FSV
toward
the

right
is

remained

only
on
the

spring

15

8

I

72

t

I

05

I
II

AT097

AT
8
Fig
AT
12

1st
2nd

shift
valve

Low
in

the

range
I
is

led
to

the
low

and
reverse
clutch
from
the

line

pressure
5

through
the
line

pressure
12
and
at
the
same
time

the
same
is
led
to
the
left
end

spring

unit

Consequently
although
the

go

vernor

pressure
increases
the
valve
is

still

depressed
toward
the

right
and

the
SFV
is

fixed
in
the
Low

posi

tion
When

kicked
down

at
the

2nd

speed
the
SDV

operates
and
the

line

pressure
13
depresse
the
FSV
to

ward
the

right

Although
the

governor

pressure
15
is

considerably
high
the

valve
is

depressed
completely
toward

the

right
and
the

FSV
is

returned
to

the
Low

position
This

operation
is

called
Kick
down

shift

2nd
3rd
shift
valve
SSV

The
SSV
is

a
transfer
vaIve
which

shifts

speed
from
2nd
to
3rd

When
the
vehicle
is

stopped
the

SSV
is

depressed
toward
the

right
by
the

spring
and
is
in

the
2nd

position
It

is

provided
however
that
the
FSV

decides
the

shifting
either

to
Low

or

2nd

When
the

vehicle
is

running
the

governor

pressure
15
is

applied
to

the

right
end
surface
and
the
SSV
is

depressed
toward
the

left

Contrarily

the

spring
force
line

pressure
3
and

throttle

pressure
19

depress
the

SSV

toward
the

right

When
the

vehicle

speed
exceeds
a

certain
level
the

governor

pressure

exceeds
the
sum
of
the

spring
force

line

pressure
and
throttle

pressure
the

valve
is

depressed
toward
the
left
and

the
line

pressure
3
is
closed
Conse

quently
the
forces

are
rapidly
un

balanced
the
force
to

depress
the
SSV

toward
the

right
reduces
and
thus
the

SSV
is

depressed
to
the
Ie
ft
end

for
a

moment

With
the
SSV

depressed
to

ward
the

left
end
the
line

pressure
3

is

connected
with
the
line

pressure

10
the

band
servo
is
released
the

front
clutch
is

engaged
and

speed
is

shifted

to
3rd

When

the
accelerator

pedal
is

de

pressed
both
the
line

pressure
3

and

the
throttle

pressure
19

are

high
and
AUTOMATIC
TRANSMISSION

therefore
the

SSV
is

retained
in

2nd
unless
ihe

governor
pressure

IS
exceeds

the
line

pressure
3
and

the

throttle

pressure
19

In

the
3rd

position
force
to

depress
the

SSV
toward
the

right
is

remained

only
on
the
throttle

pressure

16
and

the
throttle

pressure
16
is

slightly
lower
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
low

speed
side

Shifting
from
3rd
to

2nd

occurs
at

a
speed

slightly
lower

than
that
for

2nd
to
3rd

shifting

When
kicked
down
at
the
3rd

line

pressure
13
is
led
from
the
SDV

and
the
SSV
is

depressed
toward
the

right
Although
the

governor
pressure

is

considerably
high
the
valve
is

de

pressed
completely
toward
the

right

and
thus
the
SSV
is
returned
to

2nd

position
This

operation
is

called
Kick
down
shift

When
the
shift
lever
is
shifted

to

2
or
I

range
at
the

3rd

speed

the
line

pressure
3
is

drained
at

the

MNV

Consequently
the
front
clutch

operating
and
band
servo

releasing
oils

are
drained
As

the

res
lIt
the
trans

mission
is
shifted

to
the
2nd
or

low

speed
although
the

SSV
is
in

the
3rd

position

When
the

speed
is
shifted
to
the

3rd
a

one

way
orifice
24
on
the

top
of
the

SSV
relieves
oil

transmitting

velocity
from
the
line

pressure
3

to

the
line

pressure
10
and
reduces
a

shock

generated
from
the

shifting

Contrarily
when
shifted
from
3rd

to
2
or

range
and
the

speed
is

shifted
to
the
2nd

spring
of
the
orifice
24
is

depressed
the
throttle

becomes
ineffective
the

line

pressure

10
is

drained

quickly
and
thus

delay
in
the

speed
shifting
is

elimi

nated

Throttle

of
the

line

pressure
6

relieves
the
oil

transmitting
velocity

from
the

line

pressure
6
to
the

line

pressure
10
when

the
lever
is

shifted

to
the

R

range
and
relieves
drain

velocity
from
the
line

pressure
10
to

the
line

pressure
6

when

shifting

from
3rd
to

2nd
at

the
D

range
Thus
the
throttle
of
the
line

pressure
6
reduces

a
shock

generated

from
the

shifting

A

plug
in
the
SSV
left

end

readjust

the
throttle

pressure
16
which
varie

depending
on
the

engine
throttle
con

dition
to
a

throttle

pressure
19

suited
to
the

speed
change
control

Moreover
the

plug
is

a
valve
which

applies
line

pressure
13
in

lieu
of
the

throttle

pressure
to
the

SSV
and
the

FSV
when
kick

down
is

performed

When
the
throttle

pressure
16
is

applied
to
the
left
side
of
this

plug

and
the

plug
is

depressed
toward
the

right
a
slight

space
is
made
from
the

throttle

pressure
16
to

19
A
throt

tIe

pressure
19
which
is
lower

by
the

pressure
loss

equivalent
to
this

space
is

generated
the

pressure
loss
is
added
to

the

spring
force
and
thus

the

plug
is

depressed
back
from
the

right
to
the

left

When
this

pressure
19
increases

excessively
the

plug
is
further
de

pressed
toward
the
left

space
from

the

throttle

pressure
19
to
the
drain

circuit

13
increases
and
the
throttle

pressure
19
lowers
Thus
the

plug
is

balanced
and
the

throttle

pressure

19
is
reduced
in
a

certain
value
b

3
Orifice

t

checking
valve

24

15

2
2

i
I

1
c

V
Y
ii
pr

W
jt1

iff
I
W
q

I
nHH

J

L19
H
10

15

AT
9
A

T098

Fig
AT

13
2nd
3rd

shiflvalue

against
the

throttle

pressure
16

When

performing
the

kick
down

the

SOV

moves
a

high
line

pressure
is

led
to

the
circuit
19

from
the
line

pressute
circuit
13

which
had

been

drained
the

plug
is

depressed
toward

the
left

and
the
circuit

19
becomes

equal
to
the

line

pressure
13
Thus

the

kick
down
is

performed

Preasure
modifier
valve

PMV

In

comparison
with
the

operating

pressure
required
in

starting
the

vehi

ele

power

transmitting
capacity
of
the

clutch

in
other

words

required
op

erating
pressure
may
be

lower
when

the

vehicle
is
once

started
When
the

line

pressure
is
retained
in

a

high
level

up
to
a

high
vehicle

speed
a
shock

generated
from
the

shifting
increases

and
the
oil

pump
loss
also

increases
In

order
to

prevent
the
above

described

defective
occurrences
with

the

opera

lion

of
the

governor
pressure
15
the

throttle

pressure
must
be

changed
over

to

reduce
the

line

pressure
The
PMV

is
used

for
this

purpose

When
the

governor

pressure
15

which
is

applied
to

the

right
side
of

the

PMV
is

low
the
valve
is

depressed

toward

the

right
by
the

throttle

pres

sure

16

applied
to

the
area

differ

ence
of

the
value
and
the

spring
force

and

the
circuit

from
the

circuit
16
to

the

circuit
18
is

closed

However

when

the

vehicle

speed
increases
and

the

governor

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

throttle

pressure
16
toward
the

right
the
valve
is

depressed
toward
the

left
and
the

throttle

pressure
is

led

from
the
circuit

16
to

the

circuit

18
This

throttle

pressure
18
is

applied
to

the

top
of
the

PRY

and

pressure
of
the
line

pressure
source
7

is

reduced

Contrarily
when
the
vehi

cle

speed
lowers
and
the

governor

pressure
15
lowers
the

force
toward

the

right
exceeds
the

governor
pres
CHASSIS

sure
the
valve
is

depressed
back
to

ward
the

right
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

the
throttle

pressure
is

low
and
the

governor

pres

sure
is
low

II

18
16

1JU

k
I

15

AT099

Fig
AT
14
Pressure

modifier
valve

Vacuum
throttle
valve

VTV

The

vacuum

throttle
valve
is
a

regulator
valve

which
uses

the
line

pressure
7
for
the

pressure
source

and

regulates
the

throttle

pressure
16

which

is

proportioned
to
the

force

of

the

vacuum

diaphragm
The

vacuum

diaphragm
varies

depending
on
the

engine
throttle
condition

negative

pressure
in
the

intake
line

When
the
line

pressure
7
is

ap

plied
to

the
bottom

through
the
valve

hole

and
the

valve
is

depressed

up

ward

space
from
the

line

pressure
7

to
the

throttle

pressure
16
is

closed

and
the

space
from
the

throttle

pres

sure

16
to
the

drain
circuit
17
is

about
to

open
In

this

the
throttle

pressure
16
becomes
lower

than
the

line

pressure
7

by
the

pressure

equivalent
to
the

pressure
loss

of
the

space
and
the

force
to

depress

through
the

rod
of
the

vacuum

dia

phragm
is

balanced
with
the

throttle

pressure
16

applied
upward
to

the

bottom

When

the

engine
torque
is

high
the

negative
pressure
in
the

intake

line

rises

similar
to
the

atmospheric
pres

sure
and
the

force
of

the
rod
to

depress
the
valve

increases

As
the

result
the
valve
is

depressed
down

ward
the

space
from
the
throttle

pressure
16
to

the
drain

17
re

AT

lO
duces
and
the

space
from
the

line

pressure
7
to
the

throttle

pressure

16
increases

Consequently
the

throttle

pressure

16
increases

and
the

valve
is

baI

anced

Contrarily
when

the

engine

torque
lowers
and
the

negative
pres

sure
in

the
intake
line
lowers

similar

to
vacuum
force
of

the
rod

to
de

press
the

valve
lowers
and
the

throttle

pressure

16
also

lowers

When
a

pressure
regulated
by
the
throttle

back

up
valve
described
in

the
subse

quent

paragraph
is

led

to
the
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
ptessure
17
and
the
valve
is

locked

upward

bi

II
I

ATlOa

Fig
AT
15
Vacuum

throttle

valve

Throttle

back

up
valve
TBV

Usually
this
valve
is

depressed

downward

by
the

spring
force

and
the

circuit

17
is

drained

upward

As

soon
as
the
lever
is

shfted
either

to
2
or

range
line

pressure
is

led

from
the
circuit
4

the
line

pressure
is

applied
to
the
area
differ

ence
of
the
valve

the
valve
is

depres

sed

upward
the

space
from
the
circuit

4

to
the

circuit

17
is

timely
closed

and
with
the

space
from

the
circuit

17
to
the

upper
drain

being
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

the
circuit
4
to
the
circuit

17
is

balanced
with
the

spring
force

Further
when

speed
is

shifted
from

2nd
to

Low
at

the

range
I

line

pressure
is

led
from
the

circuit

12

and
the
line

pressure
is

applied

upward

to
the
bottom

of
the

valve

through
the

valve
hole

Consequently
the

valve
is

depressed
upward
and
locked
As
the

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
valve

Solenoid
downshift
valve

SDV

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
kick
down

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
circuit
from
the

line

pressure
4
to
the
line

pressure

13
is

opened

When

kick
down
is

performed
the

push
rod

operates
the
valve
is

depres

sed
downward
and
the
circuit

from

the
line

pressure
7

to
the
line

pres

sure

13
opens
The
line

pressure
13

opposes
the

governor
pressure
15
at

the
SSV
and
FSV
and

thus

performs

the
downshift

operation
AUTOMATIC
TRANSMISSION

AT102

Fig
AT

17
Solenoid

downshift
value

Second
lock
valve
SLV

This
valve
is
a

transfer
valve
which

assists

the
shift
valve
in
order
to

decide

the
fixed
2nd

speed
at
the
2

range

In
the

D

range
the
sum
of

the

spring
force
and

line

pressure
3

applied
upward
exceeds

the
line

pres

sure
2

which
is

applied
to
the

valve

area

difference
as
the

downward

force

As
the

result
the

valve
is

locked

upward
and
the

circuit

from
the
line

pressure
8
to
the

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
the
line

pressure

1
is
released

to
the
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

the
result
the

valve
is

locked

downward
the
line

pressure
2
is

released

to
9

regardless
of

the

operat

ing
condition
of
the
FSV
and

the

band

servo
is

engaged

2nd
3rd

timing
valve

TMV

This

valve
is

a
transfer
valve
which

switches
the

by
pass
circuit
of
the

AT
ll
J

2

3

ATl03

Fig
A
T
18

Second
lock

ualue

orifice
22
in

the
front
clutch

pres

sure
circuit
II
in

response
to
the

vehicle

speed
and
the

throttle
con

dition
A
force
created

when
the

go

vernor

pressure
15

applies
to
the

bottom
of
the

TMV
is

used
for
the

upward
force
and
a

force
created

when

the

spring
force

and
the

throttle

pressure

apply
to
the

top
of
the

TMV

is
used
for

the
downward
force

When
the

throttle

pressure
16
is

lower
than

the

governor
pressure
15

the

upward
force

exceeds
the
down

ward
force
the
valve
is
locked

upward

and

passage
from
the
circuit
10

2nd
from
the

Top
to
the
circuit

II
is

closed

Consequently
the

line

pressure
10
is
led
to

the
front

clutch

circuit

1
I

through
the

orifice
22

and

thus
the
oil

pressure
is
trans

mitted

slowly
However
under

the

normal

shifting
the

throttle

pressure

16
has
a

pressure
exceeding
a
certain

level
and

the
downward
force
exceeds

the

upward
force
As
the
result
the

valve
is
locked
downward
the

passage

from
the
circuit

10
to
the
circuit

1
I
is

opened
and
the

orifice
22

is

disregarded

1

i
16

I
O

11

l1
1

r

X

lp

I
15

J

AT104

Fig
AT
19
2nd

3rd

timing
ualue