1973 DATSUN B110 torque

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

AUTOMATIC

TRANSMISSION

Manual

linkage

The
hand
lever
motion

The
hand

lever
is
located

in
the
driver

s
com

part

men

mechanically
transmitted
from

the
remote
control

linkage
is
further

transmitted
to
the
inner
manual

lever

in

the
transmission

case
from
the

range

selector
lever
in

the

right
center

poc

tion

of
the

transmission
case

through

the
manual

shaft
The
inner

manual

lever
is

thereby
turned

A

pin
installed
on

the
bottom
of

the
inner
manual
lever
slides
the

manu

al

valve

spool
of
the

control
valve
and

thus
the

spool
is

appropriately
posi

lioned

opposing
to

each
select

position

The

parking
rod

pin
is

held
in
the

groove
on
the

top
of
the
inner

manual

plate
The

parking
rod

pin
operates
the

rod
at
p

range
and

operates
the

mechanical

lock

system

Moreover
the
above
described

manual
shaft
is

equipped
with
an

inhibitor
switch
A

rotor
inside
the

inhibitor
switch
rotates
in

response
to

each

range
When
the

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

rotor
closes
the

back

up
lamp
circuit
and
the

back

up

lamp
lights

Vacuum

diaphragm

The
vacuum

diaphragm
is
installed

un
the
left

center

portion
of
the

transmission
case
The

internal
con

struction
of
the
vacuum

diaphragm
is

as
follows
A
rubber

diaphragm
forms

a

partition
in
the
center
The

engine

intake
manifold

negative
pressure
led

through
vacuum
tube
and

spring
force

are

applied
to
the
front
surface
of
the

rubber

diaphragm
and

atmospheric

pressure
is

applied
to
the
back
surface

A
difference
between
pressure

applied

to

the
front
and
back
surfaces
be

comes
a

vacuum
reaction
and
thus

the
throttle
valve
of
the

control
valve

inside
the
transmission
case
is

op

erated

When
accelerator

pedal
is

fully
de

pressed
and
the
carburetor
is

fully

upened
but
the

engine
speed
is
not
1

Housing

2
Cover

3

Outer
gear
AT071

4
Inner

gear

5
Crescent

Fig
AT
3
Oil

pump

1

Manual

plate

2

Inhibitor

switch
A
TOB7

3

Parking
rod

4
Manual

shaft

Fig
AT
4

Manuallinhage

To
intake
manifold

A

TOBB

Fig
A
T
5

Vacuum
diaphragm

iV

Down
shift
solenoid
i

KiCk
down

switch

A

TOB9

Fig
A
T
6

Downshift
solenoid

AT
5
sufficiently
increased
the
manifold

negative
pressure
lowers

becomes

similar
to
the

atmospheric
pressure

and
the

vacuum
reaction

increases

since

the
flow

velocity
of
mixture

inside
the
intake
manifold
is

slow

Contrarily
when
the

engine
speed

increases
and

the
flow

velocity
of

the

mixture

increases
or
when

the
carbure

tor
is
closed

the
manifold

negative

pressure
increases
becomes
similar
to

vacuum
and
the

vacuum
reaction

reduces

Thus
a

signal
to

generate
hydraulic

pressure
completely
suited
to

the

engine

loading
at
the

control
valve
is

transmitted
from

the
vacuum
dia

phragm
and

most
suitable

speed

change
timing
and
line

pressure
are

obtained
so

that
the
most

proper

torque
capacity
is

obtained

against
the

transmitting

torque

Downshift

solenoid

The
downshift

solenoid
is

of
a

magnetic
type
installed

on
the
left
rear

portion
of
the

transmiSsion
case

When

a

driver

requires
accelerating
power

and

depresses
the
accelerator

pedal

down
to

the

stopper
a

kick
down

switch

located
in
the

middle
of
the

accelerator
link
is

depressed
by
a

push

rod
the
kick
down
switch
closes
cur

rent
flows
to

the
solenoid
the
sole

noid

push
rod
is

depressed
the

down

shift
valve
of

the
control
valve
inside

the
transmission

case
is

depressed
and

the

speed
is

changed
forcedly
from

3rd
to
2nd
within
a

certain
vehi

cle

speed
limit

Note
As
the
kick
own

switch
closes

when
the
accelerator

pedal
is

depressed
from
7
8
to
IS
16
of

the
whole
stroke
the

accelera

tor

pedal
should
be

correctly

adjusted
and
fixed
so
as
to

afford

complete
stroke

The

arrangement
of
the
switch

differs

according
the
models
of

vehicle

Governor
valve

The

primary
and

secondary
gover

nor
valves
are
installed

separately
on

the

back
of
the
oil
distributor
on

the

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

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

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

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