Datsun 1000 - LINE PRESSURE TEST

8
Automatic TrarumilJlJion
I
I When
the
stall test
speeds
are the same in
every
range
but
above
2100
rpm
and
discharge pressure
from the
oil
pump
is
normal
and there
is no
slippage
of clutch
or
band the
following
defects mav be
present
a Low oil
level in
the
torque
converter
b Oil
circulation
to the
converter has ceased
thus
allowing
the
generation
of
steam
and
air inside the
converter c
Air in
the transmission
fluid
due
to
overheating
of
the oil
TO CHECK
AND TEST
7 LINE PRESSURE
TEST
I
Should the
transmission
performance
indicate
slipping
of the
clutch band and brake
or
incorrect
speeds
during
gear change
check the line
pressure
2
To cheCK the line
pressure
remove
the
plugs
and
connect the line
pressure
gauge
to
the
measuring
points
In
the rear
flange
3 Commence the line
pressure
measurement at idle
speed
and check
by stages
through
to
throttle
range
4
High
throttle
pressure
results
in excessive
speeds
and a
sharp
thump
or
shock
during
the
chariging
up process
5
Leaking spool
valve or
gear
trains
result
in
slipping
or
faulty
transmission
performance
6 With
the line
pressure gauge
titted to the
transmission
carry
out
a
slow
idling
line
pressure
test
for the
lilll
gear range
Should low
idling
pressures
exist
in all
ranges
namely
R P I 2
and D this
condition
can be caused
by
a
defective
pressure
supply system
or
insufficient
power
due
to a
worn
oil
pump
a
sticking regulator
valve or
oil
pressure
leak in
the valve
body
or
case or
an
oil
pressure
leakage
in
the oil
pump
7 Select
ranges
I 2
and
D and check the
line
pressure
a t low i le
Should the
readings
in the three
respective ranges
be
below those
readings specified
and
pressure reading
in
R
is
within
the
specified range
the
cause of the lo
pressure
reading
can
be
attributed
to oil
leakage
in the
governor and
rear clutch
8
Select
positions
R
and P
and
check
the
line
pressure
If the
pressure reading
is below
that
specified
and
on
selecting
I 2
and
D
and
finding
that the
pressures
are as
specified
it
can be determined that the
loss of
pressure
in R
and P is
due to
oil
leakage
in
the low and
reverse brake
circuit
9
High
idling
line
pressures are
caused
by
increased
line
pressures
due
to
sticking regulator
valve and
increased
throttle
pressure
due
to vacuum tube or
diaphragm
leakage
10
To measure the vacuum
leakage
remove the
vacuum
pipe
and
measure
the
negative pressure
immediately
the
pipe
is removed
d 1
A
defective or
punctured
diaphragm
can be
determined
by
the emission of white smoke
from the
exhaust
pipe
If
the
diaphragm
is
damaged
replace
Immediately
as a
damaged
diaphragm
will
drain
the oil from
the transmission via the
manifold
12
Checking
of
line
pressure
iitcrease
should be
carried out in
conjunction
with
the STALL TEST
Using
a
vacoum
gauge
with a
range
from 0 rum
Hg
300
rum
Hg
carry
out the
necessary
tests
13
Should the line
pressures
fail to
increase with
the
vacuum
decreasing
then check the
vacuum rod connection
14
Faulty
line
pressures
are
due
mainly
to a defective
pressure regulator
valve
plug or
pressure
regulating
valve
View of Automatic Transmission
with Oil Pan Vacuum
Diaphragm Assembly
and Down Shift
Solenoid Removed
80
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