THE
AUTOMATIC TRANSMISSION
•
•
•
•
The regulator valve controls the main line pressure, a
secondary piston on the valve boosts this pressure when
reverse
is
selected.
The governor
valve
movement
is
controlled by the
mechanical governor and it directs the oil
flow
to the
appropriate clutch or servo for automatic gear-shifts.
The relay valves are used for shifts from second to third
and third to top. They enable the clutch or servo required
to be supplied either from the selector valve in 'manual'
control or the governor valve in 'automatic'. In addition,
pistons are fitted in front
of
the second and third relay
valves to ensure that on up-shifts the engagement
of
the
new
ratio and release
of
the old occur simultaneously
to prevent engine overspeeding between shifts. A relay
valve
is
not required for the first gear as the torque
reaction is controlled mechanically by a one-way clutch.
MINI. Issue
1.
4908
Fa
The tow-start valve short-circuits the auxiliary pump
under all normal driving conditions but supplies the
required line pressure for tow-starting. Immediately the
engine starts the main pump automatically takes over.
The low-pressure
valve
This valve controls the pressure in the converter to
30
lb./sq. in.
(2·1
kg./cm.
2
).
When the engine
is
stopped
the valve
is
seated, preventing the converter draining.
This avoids difficulties in checking the combined engine/
transmission oil
level
and prevents a noisy and inefficient
converter when restarting the engine.
The
auxiliary
pump
This unit
is
used for tow-starting.
It
is
of
limited
capacity and
is
responsive to road speed only.
Fa.3
mk1-performance-conversions.co.uk
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