1973 DATSUN B110 brake

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

AUTOMATIC
TRANSMISSION

HYDRAULIC
SYSTEM
AND

MECHANICAL
OPERATION

The

operating
system
of
oil

pres

sure
in
each

range
is

described
below

The
oil

pressure
in
each
circuit

shown
in

the
illustration
is
classified
as

follows

according
to
the
function

The
numerals

show
the
circuit

num

bers

Pressure

source
of

the
line
7

Operating
line

pressure
for

friction

elements

I
2
3
4
5
6

8
9
10
II

12

Auxiliary
line

pressure
13

Pressure
of

throttle

system

16
17

18
19

Others
14
15
t

AT106

Fig
AT
22
ld

Jltification
of
oil

channels
in
case

front

fac
e

Discharge
hole
of
oil

pump
7

Torque
c

nver

pre
ure

14
co

t
Re
r

lutch

pressure
l

Front
clutch

pres5ure
II

I

c
Suction
hole

of

t
o

ump

lUlJJl
0
o

f

Governor

Dl5charge
hol
of
011

pUf
lP
7

pressure
15

I

II

nl

1F
Jl

r
Torque
converter
o

L
U

pres
ure
14

It
0
Servo
release
i
I

prc
sUre
IO

Rear
clutch

Servo

L

i

pres
ure

I

0

6
tightening
19

iressu
9
01

Front

clutch

rJj
low

reverse

pressure
II
0

C

lrv
brake

pressure

Suction
hole
of
oil

pump
s

6od
OJ
12

Governor
feed

pressure
I

ATlOS
AT101

Fig
AT
21

Identification
of
oil

channels
in
oil

pu
mp
Fig
AT
23

Identification
of
oil

channels
in
case

face

AT
13

1

range
Park

The

operation
of
clutches
and
band

are

functionally

quite
the

same
as
in

Neutral

In

parking
however

as
the

parking

pawl
meshes
in
a

gear
whkh
is

splined

to
the

output
shaft
the

output
shaft
is

mechanically
locked
from

rotating

The

oil

discharged
from
the

oil

pump
is
fed
to
each

part
in
a
similar

manner
to
that
of
the

N

range
The

oil

having
the
line

pressure
7
which

has
been

introduced
to

the
manual

valve

V
reaches
the
I
st
2nd

shift

valve

ID
through
the
line

pressure

circuit
5
As

the
1st
2nd

shift

valve
is
forced
to

the

right
hand
side

by
the

spring
the

line

pressure
5
and

I2
actuates
the
low

and
reverse

brake

through
the

groove
Also
the

parking
pawl
engages
with
the
au
tee

teeth

of
the
oil

distributor

by
the

manual
lever

mechanically
locking
the

output
shaft
CHASSIS

Free
Lock

I

l

J

1

ri
r
r0
1

1
J

r

A
T086

Fig
AT
24

Parking
mechanism

Ceo
Clutch
Low
Band
rvo
One

Parking

RanKe

atia
rever
w

y

pawl

Front
RUI

brake
Operation
Release

clutch

Park

Reverse
2
182
on
on

Neutral

01
Low
2
458
on

Drive
02
Second

1
458

03

Top
1
000
on

2
Second
1
458
on
on

12
Second
1458
on

II
Low
2
458
on

AT
14

AUTOMATIC
TRANSMISSION

P

range
Park

Torque
Converter
Low
R

Brek

Brake

Sand

I

1
VOO
O

Solenoid

C

iT
A

q

r
CMo

I

I
U1

t5
I

j

I

T
CQ
r
C

A
uIUi
g
Velv
Bend

i

Servo
1f

a

riealion

11

11111
J
I
2

CID
v

f
0

1

J

fI
I

I
1
O

II

II
CID
Solen
iO

Cow
lift
I

J

II

I

Front

Lubrical
n

v

n
1

j
III

r
I
1

II

Orifice
18

C

tt

J
v

2
5
Mod

I

I

1
1

I

J
5JJ

if
1
@
2nd
3rd

Timing

I

1l
If

m

t

I
r
I

m

II
I
I

I

II

R
vuletor
Valve

II
U
L
J
l2
23

6

@
Menuel

Vel

P
R

N
D

2
I

fl31
i

I

I
I

I

l

I
Throttl

Dr
n

Valy
T

o

u

g

Il

I
d

Not
Jhorklld
Cu
in

lsur
Go
ernor
1
1
litHe

OICondery

Gov
norVelYe
Primary

Gov
no

1

Governor
ur

T
eMU

H

Fig
A
T
25
Oil

pressure
circuit

diagram
P

range
Park

AT
15