1979 DATSUN 210 automatic transmission

The
3N71
B
trammission
is
a

fully

automatic
unit

consisting
primarily
of

a
3
element

hydraulic
torque
converter

and
two

planetary
gear
sets
Two

multiple
disc
c1utclies
a

multiple
disc

brake
brake

band
and
one

way
clutch

provide
the

friction
elements

necessary

to
obtain

the
desired
function
of
the

two

planetary
gear
ets

A

hydraulic
control

system
is

used

to

operate
the
friction
elements
and

automatic
shift
controls

TORQUE
CONVERTER

The

torque
converter
is

attached
to

the
crankshaft

through
a
flexible
drive

plate
Heat

generat
in
the

t
rque

converter
is

dissipated
by
circulating

the
transmission
fluid

through
an
oil

to

water

type
cooler
in

the
radiator

lower
tank

The

welded
comtruction

of
the

torque
co
verter

prevents
di
3

ssembly

or
service
unless

highly

specialized

equipment
is
available

Qj
gJ
Autpmatic
Trimsmissi6n

DEScRIPTION

FLUID

RECOMMENDAnON

Use
DEXRON

type
automatic

transmission
fluid

only

IDENTIFICATION
NUMBER

Stamped
position

The

plate
is

attached
to
the

right

han
side
of
transmission

case

AT
M

Fig
AT
l

Identification
Number
Identification
of
number

arranaemanta

JAPAJllUTOIlATlC
TRAJISIIISSIO

C8
Ull

MODEL
X
0
12
3

NO
7
6
0

1
2

34

Number

designation

76
0
I
2

34

L

Serial
productioo

number

for
the
month

Month
of

production

1
Jan

2
Feb

X

Oct
Y

Nov
Z

Dec

Lut

IJgUre
denotins

the
year
A

D

IJ

III

J

W

f

r
lrr

G

1

Transmission
case

2
Oil

pump

3
Front
clutch

4

Band
brake

5
Rear
dutch

6
Front

planetary
geat

7
Rear

planetary
gear
8
One
way
clutch

9
Low
4
Reverse
brake

10
Oil
distributor

11
Governor

12

utput
shaft

13
Rear
extension
14
Oil

pan

IS
Control
valve

16

Input
shaft

17

Torque
converter

18
Converter

housi

19

Drive

pia
te
Tightening

torque
T
of

bolts
and
nuts

kg
m
ft
lb

@
T
4

to
5
29
to
36

@
T

14
to
16
101

to
116

@
T
4

5

to
5
5

33
to
40

@
T

0
6
to
0
8
4

3
to
5

8

@

T
0
5
to
0
7

3
6
to

5
1

T
2

0
to
2
5

14
to
18

@
T

1
3
to
1

8
9

to
13

@
T

0
55
ta
0
75
4
0
to
5
4

CD
T

0
25
to
0
35
1
8
to
2
5

AT312

Fig
AT
2
3N71B

Automatic
Trammiuion

AT
2

Automatic
Transmission

HYDRAULIC
CONTROL
UNIT
AND

VALVES

The

hydraulic
or
a
tomatic
control

system
is

comprised
of
four
4
basic

groups
the

pressure
supply
system

the

pressure
regulating
system
the

flow
control
valves
and
the
friction

elements

PRESSURE
SUPPLY
SYSTEM

The

pressure
supply
system
consists

of

a

gear

type
oil

pwnp
driven

by
the

engine
through
the

torque
converter

The

pump
provides

pressure
for
aU

hydraulic
and
lubrication
needs

PRESSURE
REGULATOR

VALVES

The

pressure
regulating
valves
con

trol
the

output
pressure
of
the
oil

pump

Pre
ure

rellulator
valve

The

pressure
regulator
valve
con

trois
mainline

pressure
based
on

throttle

opening
for
the

operation
of

the
band
clutches
and

brake

Governor

valve

The

governor
valve
transmits

re

gulated
pressure
based
on
car

peed

to
the

shift
valves
to
control

upshifts

and
downshifts

Vacuum
throttle
valve

The
vacuum

throttle
valve
transmits

regulated
pressure
based
on

engine

load
vacuum
This

pressure
controls

the

pressure
regulator
valve

Also
this

pressure
is

applied
to
one
end
of
the

shift
valves
in

opposition
to

governor

pressure
which
acts

on
the
other

end

of
the
shift
valves

controlling

upshift

and
downshift

speeds
FLOW
CONTROL
VALVES

Manual
valve

The
manual
valve
is
moved

manual

Iy
by
the
car

operator
to
select
the

different
drive

ranges

1
2
ShHt
valve

The
1
2

shift
valve

automaticaIly

shifts
the
transmission
from
first

to

second
or
from
second
to
first

depend

ing

upon
governor
and
throttle

pres

sure

along
with

accelerator

position

solenoid
downshift
valve
See

Hy

draulic
Control
Circuits
Drive

2

2
3
ShHt
valve

The
2
3
shift
valve

automaticaIly

shifts
the
transmission
from
second
to

top
gear
or
from

top
to
second
de

pending

upon
governor
and
throttle

pressure
or
accelerator

position
sole

noid
downshift
valve

See
Hydraulic

Control
Circuits
Drive
3

Range

2
3

Tlmlnll
valve

For
2
3
shifts
a
restrictive
orifice

slows
the

application
fluid
to
the
front

clutch
while
the

slower

reacting
band

is
allowed
to
release
This

prevents
a

hard
2
3
or
3
2
shift
Under

heavy

load
however
the

engine
will
tend
to

run

away
during
the
2
3

or
3
2
shift

pause
therefore
a
2
3

timing
valve

using
throttle
and

governor

pressure
is

used
to

bypass
the

restrictive
orifice

during
such

heavy
load
conditions

Solenoid
down
hHt
valve

The
solenoid
downshift
valve
is

activated

electrically
when
the
ac

celerator
is
f1oor
d

causing
a
forced

downshift
from

top
to
second

top
to

first
or

second
to

first

gear
depending

upon
car

speed
governor

pressure

AT
3
Pre
ure
modified
valve

The

pressure
modifier

valve
assists

the
mainline

pressure

regulator
valve
in

lowering
mainline

pressure
during

high

speed

light
load
conditions
such
as

steady

speed
cruise

Governor

pres

sure

working

against
a

spring

opens

the

valve
which
aUows

modified
throt

tle

pressure
to
work

against
the

pres

sure

regulator
valve

spring
lowering

mainline

pressure
Lower

operating

pressure
under

light
load

reduces
oil

temperature
and
increases
transmis

sian
life

Throttle
back
up
valve

The
throttle

back

up
valve
assists

the
vacuum
throttle
valve
to

increase

line

pressure
when
the
manual
valve
is

shifted

either
to

2
or
I

range

Second
lock
valve

The

second
lock
valve
is

used
to

bypa
the
1
2

shift
valve

to
maintain

the
band

apply

pressure
in
2

posi

tion
The
valve
is
also
used
as
an
oil

passage
for
the
1
2

shift
valve

band

apply

pressure
in

D2

D3
and

12
Range

CLUTCHES
AND
BAND

SERVOS

The

servo

pistons
of
the
clutches

low

reverse
brake
and

band
are
moved

hydraulically
to

engage
the

clutches

brake
and

apply
the
band
The
clutch

and

brake
istons

are
released

by

spring
tension

and
band

piston
is

released

by
spring
tension

and

hy

draulic

pressure

Automatic

Transmission

IT
Tl

l
fT
TI

c
t

Ii
i

u6

01

r

Io

I

J
J

li
jJ
lUJ
1
d

AT090t

I

Pressure

regulating
valve

2

Manual
vahe

3

ht
2nd
shift

valve

2nd

3rd
lhift
valve

S
Pressure

modifier
wive
6
Vacuum

throttle
valve

7
Throttle
back
up

valve

8
Solenoid
down

shift
valve

9
Second

lock
valve

10
2
3

timing
valve

Fill
A
T
3
Control

Vol

AT
4

OIL
CHANNEL

IDENTIFICATION

The
circuit
numbers
shown
in
each

Hydraulic
Control
Circuit
are

classified

as
follows
according
to
the

function

Pressure
source
of
the
line
7

Operating
line

pressure
for

friction
elements

I
2
3
4
5
6

g
9

10
11
12

Auxiliary
line

pressure
13

Torque
converter

pressure
14

Governor

pressure
15

Throttle

system
pressure

16
17
18

19

Oil
pump
discharge
hole
7

f
Torque
converter

pressure
14

Rear
clutch

pressure
1

Front
clutch

pressure
11

W
h0i1
pu
6
suction
hote

e

8

IIlIlJJIII
Automatic
Transmission

L

f

AT106

Fig
AT
5

Oil
Channela
in
Cou
Front
Face

lo
o

o
0

Oil

pump
discharge
hole
7
Governor

pressure
15

1

h

Torque
converter
I

pressure
14
0
0

Servo
release

Rear
clutch

l
press
re

10
r

L

Governor
reed

pressure
1

pressure
1
Servo

tlghtemng

li
nb

o

0

pressure
9

r

Front

clutch
fI
Low
reverse
brake

pressure
12

pressure
11

U
0

111
1

1
P
u
n

e

AT107

ATlOS

Fig
A
T
4

Oil
Channell
in
Oil
Pump
Fig
A
T
6
Oil
Channell
in
Cou
Fac

MECHANICAL
OPERATION

In

the
3N71B
automatic
transmis

sion
each

part
operates
as
shown
in

the

following
table
at
each
gear
select

position
RanKe
Cm

ratio
Clutch
Low
A

Front
Rear

brake
One

w

y

dutch
Parkin

pa
l
Band
servo

Operation
Release

Park
on
on

Reftrst
2
182
on

on
on

Neutral

Dl
Lo
2
458
on

on

Drift
02
Second
1
458
on

03

Top
1
000
on
on
on

2
Second
1
4
8
on
on

12
Second
1458
on
on

Low
2
4
8
on
on

Note
The
low
brake
is

applied
in

11
raiW
to

prevent
free
whee6ng

when
coasting
and
aIlows
engine

braking

AT
5

Automatic

Transmission

HYDRAULIC
CONTROL
CIRCUITS

P
RANGE
PARK

Po
r
flow

In

P

range
the
shift

linkage

actuated

parking
pawl
meshes
in
a

gear

splined
to
the

output
shaft

preventing

movement
of
the

car
When
the

engine

is

running
the
low

and
reverse
brake
is

applied
by
pressure
from
the
manual

valve

passing
through
the
1
2
shift

valve
Free
Lock

II

AT086

Fig
AT
7

Parking
M
haniml

FI
1d
flow

Manual
Valve
4
Downshift
Valve
13
2nd

3rd
Shift
Valve

L

1st
2nd
Shift
Valve

Throttle

Back

up
Valve

5
1st
2nd

Shift
Valve
12

I
Throttle
Back

up
Valve

Y
Low
Reverse
Brake

I

AT
6

P
r
n
P

rk

Torqu
con
r1lr

011
cool

Drain

volv

r
Front

lubricatic

Ora

1

x

j

L

u
2

6

CD
pr
u

II
ator
Automatic
Transmission

Lawand

b
r
kr

Brah

bond

f

12@

J
f
di
X

Ivacuum
r

11
throttl
Throttl

lenOI

I
I
yo
lv

e
f
k

UP

j
o
n

1
I

s
I

j

I
c
u
u

00
0

I
1
2
@

r

13

@2nd
3rdShlft

10
lv

In
Jl

Si
R

or

clutch

x

Otific

chick

volv

Throttl

drain

01

x

II
5

I

J

1
11

II
2

@l
2

dl
r
Shift

u
I

I

j2

II

Xu
J

I

f1
11
U

2
n

Ol
l

I

I

X
X

Secondary
Primary

90
rn01

101
90
nor

01
Not
Mark

d
X
ore

drain

lint
pru
r

Go
nor

f
d
p
u
ur

Govtrnor

prusu

r
r

cl

Torqu
convert

p
ur

TI
I
ratt

prUlur
AT455

Fig
A
T
B
Oil

Pre
re

Circuit

Diagram
P

rang
Par

AT7

Automatic

Transmission

R

ren
e

Rever

Torque
con
r1

ril
j

j

I

f
I

12
C
I

J
111
x
J

0

8

Q

I

II

lr

Vacuum
Throttl

I
old

I
10
J

f
k

JP

L
u
I

lJ

El
J
U

I
II
O
co
l

chell

01

TO

I
drain

fol

il

Xl

tJj

1
J

l
2nd

3rd
Ii

minQ

x

U1
1

21
1

1C
ll

IIF

li@S
OC

II
to
0

r

6

9r3

Q

rm
g

L
1

u
iii

uLrt
23

r

t

@

PRND2
I

I
x
moo

la
OlenOid

Oil
cooler

1Rear
lubr
c

otion

f

L
ohl

r
Front

u

J

I
@2nd
3

Shift

vol

a
IS

I

12

u

l
r

I
3

w

q

r
4

I
l

Secondory

Qo
rnar

01
Primarf

Qo
i1lr
lol

Note
Mork

d
X
Qr

droin

j

Lin

prUltfrt
Go
nor

tced

r
rr
uur

J

G
0
1
1
101

pr
L
J

3
J

Torqu
can
tar

P
Urt

Tn
rotU

pr
ur

AT456

Fig
AT
10
Oil
Pr

lSure
Circuit

Diagram
R

range
Reverse

AT
9

N
RANGE

NEUTRAL

Po
r
flow

In

N

range
no
friction

elements

are
in

thus

no

power
is

tranS

milled
to
the

output
shaft
Automatic
Transmission

AT10