1975 Datsun 280z FSM - Spooled up Racing

Automatic Transmission
"1 " RANGE (LOW GEAR)
When starting in "1" range, the
.driving gear is locked to the low gear
ratio.
In "1" range, the rear clutch is
engaged and the low and reverse brake
holds the connecting drum and rear
planet carrier from rotating. The
power flow takes place through the
input shaft and into the rear clutch.
Rotation of the rear clutch drives the
rear clutch hub and front internal gear.
The front internal gear rotates the
front planetary gears clockwise to
cause the sun gear to rotate counterclockwise.
Counterclockwise rotation of the
sun gear turns the rear planetary gear
clockwise.
The rear planet carrier splined to
the connecting drum is held from
rotating by the low and reverse brake.
The clockwise rotation of the rear
planetary gears therefore rotates the
rear internal gear and internal drive
flange. The internal drive flange is
splined to the output shaft and rotates
the output shaft clockwise. However,
the output shaft rotates at a lower
speed compared to that of the input
shaft. This is caused by the fact that
the front planet carrier rotates at the
same speed as the output shaft in the
same direction since the carrier is
splined to the output shaft. The front
internal gear and planetary gear assembly
are rotating in the same direction,
but the planet carrier is rotating at a
speed slower than the ring gear. So the
gear ratio of this speed range is a
combination of the ratios provided by
the front and rear planetary gear assemblies.
Park
Reverse
Neutral
Dl Low
Drive D2 Second
D3 Top
2 Second
AT076
Fig. AT-43 Power transmission during "1 I "range
AT077
Fig. AT-44 Operation of each mechanism during "li "range
Gear
ratio
2.182
2.458
1.458
1.000
1.45 8
Clutch
Front
on
on
Rear
on
on
on
on
Low &
reverse
brake
on
on
Operation
on
(on)
on
Band servo
Release
on
on
One
way
clutch
on
Parking
pawl
on
1
] 2 Second
1 j Low
1.458
2.458
on
on
on
on
When the manual valve (2) is positioned
at "1", the line pressure (7) is
applied into the line pressure circuits
(1), (4) and (5). The oil pressure in (5)
actuates the low and reverse brake
after being introduced into the circuit
(12) through the "lst-2nd" shift valve
(3) , and the line pressure (1) acts on
the rear clutch and governor. The line
pressure (4) acts in the same manner as
in "2" range.
Similar to that of the "D" range,
the line pressure increases with the
degree of accelerator pedal depression,
and the line pressure decreases with
the increase of car speed. The governor
AT-30
pressure (15) which acts on the
"1st-2nd" shift valve does not increase
until it overcomes the combined force
of the line pressure (12) and the
spring, causing no "lst-2nd" speed
change.