Hudson 1955 Rambler, Technical & Service Manual

Page: 233 / 292

pressure on the reaction piston as well as
spring pressure. When the valve spool is in
the centered position, it directs oil pressure
to both sides of the power cylinder. The oil
return ports are also partially open so there
is relatively low pressure in the system. This
is an open center system in which the oil
pressure is variable depending upon the amount
of effort that is required to turn the wheels
(Fig. 19).
When a left turn is made, the movement of
the pitman arm stud shifts the valve spool to
the right. The valve spool opens the pressure
port and closes the return port to the right
side of the power cylinder. The return port
is opened and the pressure port is closed to
the other side of the power cylinder. The oil
pressure then moves the cylinder and valve
assembly providing power assistance. Dis-
placed oil from the power cylinder is returned
to the reservoir through the right groove of
the valve spool.
Oil pressure is also directed from the left
groove through a passage in the spool to the
reaction piston. This oil pressure is equal
to the oil pressure present in the left hand
groove in the spool. Therefore, as soon as the
pitman arm stops moving, the spool is hydrau-
lically and spring centered, and power assis-
tance is stopped.
Actually the turning effort on the steering
wheel must overcome the spring and oil
pressure on the ends of the spool before the
spool can be moved which results in a sense
of "feel" for the driver (Fig. 20).
The right turn operation is accomplished in
the same manner as the left turn with the
exception that the valve spool is moved to the
left (Fig. 21).
Disassembly and Assembly Procedure
Removal
Disconnect the oil hoses, the piston rod
from the side sill bracket, and the tie rods
from the cylinder and valve assembly.
Remove the pitman arm stud adjusting nuts,
washers, cushions, and spacers. Remove the
cylinder and valve assembly from the pitman
arm stud for bench overhaul. The pitman arm
stud is permanently attached to the pitman arm
on the "Hornet" Series.
Control Valve
Punch mark the end plug to insure accurate
reassembly and remove the plug.
Tap the end of the assembly on a block of
wood to remove the valve components. Do not
pry on any of the valve units; nicking or
scratching may result.
Do not disturb the inner plug. It is factory
installed and staked in position. Changing
this plug location will change the spool to
port alignment in the neutral position.
The "Hornet" valve spool inner components
may be replaced in service as well as the "0"
rings. However, the valve spool is not
supplied due to the possibility of improper
spool to port alignment of the replacement
part.
FRONT SUSPENSION - STEERING GEAR SECTION 11
FIGURE 19 — Schematic Oil Circuit — Centered Position