1977 DATSUN PICK-UP lock

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
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

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

2nd
3rd
timln
valve
TMV

This
valve
is
a
transfer

valve
which

switches
the

by

pass
circuit
of
the

orifice
22
in
the
front
clutch

pres

sure
circuit

II
in

response
to
vehicle

speed
and
throttle
condition
A
force

created
when
the

governor
pressure

IS
is

applied
to

the
bottom
of

the

TMV

constitutes
the

upward
force

and

a
force

created
when
the

spring

force
and
the
throttle

pressure
are

applied
to
the

top
of
the
TMV
consti

tutes
the
downward

force

When
the
throttle

pressure
16
is

lower
than
the

governor

pressure
IS
Automatic
Transmission

the

upward
force
exceeds
the
down

ward
force
the

valve
is
locked

upward

and

passage
from

circuit
l0
2nd

from
the

Top
to

circuit
II

is

closed

Consequently
the
line

pressure

10
is

led
to

the
front
clutch

circuit

II

through
the
orifice
22

and
the

oil

pressure
is
thus

transmitted

slowly

However
under
normal

shifting
the

throttle

pressure
16
has
a

pressure

exceeding
a
certain

level
and
the

downward
force
e
xceeds
the

upward

force
As

a
result
the
valve
is

locked

downward
the

passage
from

circuit

10
to
circuit

II
is

opened
and
the

orifice
22
is

bypassed

ATll
AT104

Fig
JlT
19
2nd
3rd

timing
valve

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

Automatic
Transmission

P

RANGE
PARK

The

operation
of
clutches
and

band

are
functionally
the
same
as
in

Neu

tral

In

parking
however
when
the

parking
pawl
meshes
in

a

gear
which
is

splined
to

the

output
shaft
the

output

shaft
is

mechanically
locked
from

rotating
Free
Lock

AT086

Fig
AT

24

Parlling
mechanum

The
oil

discharged
from
the
oil

Low
Band
ervo
On

pump
is

fed
to
each

part
in
a

similar
Gw
Clutch

Parkin

Range

atia
Il

Yer5e

r

pawl

manner
to
that
of
the
N

range
The
Fron
Rear
brakt

Operation
Release
clutch

oil

having
the
line

pressure
7
which

Park
on

has
been
introduced
into

the
manual

valve

Il
reaches
the
I

st
2nd
shift
Re
er
2
132
on
on
on

valve

CID
through
the
line

pressure

circuit

5
As
the
1st
2nd
shift
Neutral

valve
s
force
to
th

right
hand
ide
PI
L
w
2
3
on

by
the

spring
the
line

pressure
5
and

Drive
P2
Second
14S3
on
on

12
actuates
the
low
and
reverse

brake

through
the
groove
Also
Ihe
03

Top
1
000
on
on

parking
pawl
engages
with
the
outer

2
Second
1
458

teeth
of
the
oil
distributor

by
means

of
the

manual
lever
mechanically
12
Second
1458
on
on

locking
the

output
shaft

II
Low
2
453
on

AT
14

P

range
Park
Automatic
Transmission

L
A

r
k

8r
k

I

f

I
CID
VK

TIlro

V
lv

I
I

2
ID
Mocl

1
5
FrOl
ll

Clutch
Au

rr
tth

1
1
1

r

I

r

D

II

R
tOl
V

II

L

I
Torqu
Con
ter

0

I
ump

4

011
Coo

AM
Lubr
tlo

D
i

t
V

l

Front

o
v

n
Llrll

rt

Not
rk
t
to

Sol
n

BI

Cow
1ft
v
t

1

j
I

1111

II
I

I

il
1111
III

r
Orlflc

K

v

Throttl

Dr
ln

v

II

11
5

@
2nd
3
d

Timing

I

V
l
w
J

I
JQ

l
r
R

II

I

IKOnd
Lock

V
l

I

3J

I

t
rJ
I

q

I
rr

u

J2
3

n

l
l
J

r
A
J1

J
I

I
V
nu
l

V
l

P
21

Or
ln

LlMl

pr
r

100
10r
1

I

rlmarv

OoverrwJf
VIIfve
BIeOM
IV

OOll
nor
Y
M

Oo
or
It

Torqu
conv
ner

Throttl

Fig
A
T
25
Oil

pressu
circuit

diagram
P

range
Parh

AT
15