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PART 7-1 AUTOMATIC TRANSMISSION
(Borg-Warner)
7-7
against spring pressure under the
influence
of governor pressvre.
This allows control pressure to
reach the apply side of the front
servo.
The frcnt band thus ap-
plied together with the front clutch,
provides second gear.
With the downshift valve cam
in
the forced throttle position, forced
throttle pressure acts upon the
fint
to second and second to
third
valves so further delaying upward
changes or providing
a second to
first change at speeds when there
is little governor pressure.
Power Flow.
Again
the
front clutch
is
applied
connecting the converter turbine to
the forward sun gear.
The front band is contracted
which holds the
rev~rse
sun gear
stationary with the result that the
planet pinions
"walk"
around the
sun gear, causing the carrier
to
revolve in the same direction as
the forward sun gear so that the
ring gear is driven faster than in
first gear. The gearset provides the
redflction of 1.45 to 1.
Top Gear with "D" selected
Hydraulic Circuits
Pressure control is similar to
second gear with
"D"
selected, ex-
cept that with minimum throttle
no throttle pressure or modulated
throttle pressure acts upon the two
ends of the primary regulator valve.
Change control
is
provided by
the second to third valve moving
against spring pressure inftuence.
This ·allows line pressure to
reach the rear clutch direct, to-
gether with front servo release pres·
sure directed through the servo
orifice control valve.
When gov-
ernor pressure is in evidence, the
servo orifice control valve closes,
forcing front servo release pres-
sure through an orifice which thus
affects the relationship between
rear clutch apply and front servo
release
in
accordance with road
speed.
Since the release side of the
front servo has a larger area than
the apply side, the front servo dis-
~ngages
the band. The rear
clute~
now engaged, in conjunction with
the front clutch, provides third
gear. The absence of throttle pres-
sure, as previously mentioned, ,will
cause the second to third valve to
move early under the governor
pressure
inftuence,
so providing a
low speed second to third change.
Power Flow.
Once more the front clutch
is
applied, so oonnecting the con-
verter turbine to the forward
sun
gear.
The rear clutch is applied,
connecting the converter
turbine
to the reverse sun gear also. Rela-
tive movement of the various gears
in the gear train is impossible and
therefore the gear set revolves as
a unit, providing
a
ratio of
1
to
1.
"R" Reverse
Hydraulic Circuits.
Pressure control of the pump
IS
similar to "P" or "N".
But, according to the amount
that the accelerator pedal is de-
pressed, throttle pressure is directed
to the spring end of the primary
regulating valve, thus
increasing
control pressure in relation to
torque capacity requirements.
The manual valve directs
con-
trol pressure through the first to
second valve to the rear servo, and
control pressure through the second
to third valve to the rear clutch
and front servo
release.
Due
to
absence of governor pressure,
the
shift valves and servo orifice con-
trol valve do not operate
in this
selector position.
Power Flow.
The
rear
clutch is applied so that
the converter turbine is connected
to the reverse sun gear, whilst the
rear band is applied, locking the
planet carrier stationary. The drive
is then transmitted to the ring gear
by the outer planets. The reverse
sun and ring gears rotate in op-
posite directions with a reduction
of 2.09 to 1.
"P" Park
With the engine running, the
operation of the hydraulic
system
is identical to
"N"
except that
the
manual valve directs control pres-
sure to tt.e rear servo, although this
servo does not perform any func-
tion in "P"
No ,power is transmitted since
the clutches and bands
are
re-
leased. However an internal link-
age from the manual valve detent
lever engages the parking pawl
with teeth on the output
shaft
ring
gear.
Kickdown to Second Gear 'D'
Selected (30-50 mph approxi-
mately).
With the accelerator depressed
to
kickdown position, throttle
pressure
is applied
to the 2-3
valve and plun-
ger at line 11. Throttle pressure and
spring pressure overcome the gover-
nor pressure on the end of the 2-3
shift valve and the valve moves to
second gear position.
The front servo release and the
rear clutch apply circuits are now
exhausted via line 7 at the manual
valve.
The transmission will now
stay
in
second
gear until road speed drops
below 30 mph, when first gear will
be
selected
or governor pressure
overcomes throttle and
spring
pres-
sures and moves the valve to third
gear position.
The power !low is the same as in
second gear 'D'.
Kickdown to Low in 'D' (below
30 mph approximately).
With the accelerator depressed
to
kickdown position, the 2-3 shift
valve
is
forced to take up 2nd gear
position as described in preceding
paragraph.
Simultaneously, throttle pressure
is applied to the
small
end of the 1-2
shift valve
via
lines
11
and lOA.
Throttle pressure combined with
spring pressure will overcome gover-
nor pressure
(under
approximately
30 mph) and the
valve
will be forced
to take up first gear position. As a
result, the front servo apply circuit
will be exhausted at the 1-2
valve.
The vehicle is now in first gear and
will not change up until governor
pressure overcomes the throttle and
spring pressures and moves the valve
to second gear position.
Power flow is the same as in first
gear 'D'.
OPERATION
OF THE RANGE
CONTROL VALVE
G.T.A. SHIFT
PATTERN
(Refer Fig. 18).
'1' -
Control pressure, from line
6 at manual valve is directed to the
1-2 shift valve where it is redirected
to the rear servo apply.
At the same time control pressure
is directed from line 1 to line 5 at
the manual valve and to the front
clutch apply and governor feed lines.
Governor pressure is fed to the
range control valve at line 2 where
it feeds line 22. Line 22, governor
pressure, is directed to the large end
of the 1-2 shift valve, where it is
opposed by control pressure from
line 6,
throttle pressure from 10, and
spring pressure which holds the 1-2
shift valve in first gear position.
'2' -When 2 is selected manually,
control pressure is applied to the
front clutch and governor from line 5
at the manual valve.
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