Buick LeSabre 1965 Service Manual page 476

8 - 1 2 POWER STEERING STEERING GEAR, STEERING COLUMNS A N D LINKAGE
_ VALVE BODY CAP
\ VALVE BODY
•SSI
UB
r
PRESSURE PORT
• 1
A 1 RETURN PORT- /
m^ m m j i t X^
M
*m*/M
•Hair
^ ^ ^ ^ ^ ^ ^ ^ 8 » \ L VALVE
^ ^ ^ ^ ^ ^ ^ ^ ^ H BODY RINGS
HHHHB
VALVE SPOOL
SPRING
' - . DAMPER O-RING
TORSION
BAR
^ O-RING
ay
sssnd
3\
STUB SHAFT-J \
\ - TORSION BAR
Figure 8-15—Rotary Valve Assembly
stub shaft is attached to the up-
per steering shaft through the
flange assembly. The lower flange
is splined to the stub shaft and is
retained by a pinch bolt. The
torsion bar is l o c a t e d in the
center of the stub shaft. The
valve spool i s an open center
valve and i s positioned on the
lower end of the stub shaft. The
valve body encloses the valve
spool. The valve body cap is lo-
cated at the lower end of the valve
body.
The valve body has two large oil
grooves around its outside dia-
meter. Each groove h a s four
holes drilled into the inside dia-
meter of the valve body. The low-
er groove is lined up with the
pressure port in the gear housing.
The upper groove is lined up with
a drilled passage in the housing
which directs oil to the right turn
chamber in the housing, located at
the lower end of the rack-piston
nut. Three valve body Teflon
rings provide leakproof seals for
the oil grooves on the valve body.
The inside diameter of the valve
body has eight slots machined in
it, four are connected to the pres-
sure groove by the four drilled
holes. S e e Figure 8-16. The
other four slots, which are wider,
are connected to the return port
in the housing through the valve
spool. Near the center of the
valve body are four other drilled
holes which are used to direct oil
to a passage in the housing that
opens to the left turn chamber.
This chamber is located at the
upper end of the rack-piston nut.
The valve spool which fits inside
the valve body may have an out-
side diameter as low as only
PRESSURE SLOT (4)
RIGHT TURN
HOLE (4) " > % j
3fc
V A L V E B O D Y - ^ ^ ^ I
mm*
EFT TURN HOLE (4)
^ ^ _ RETURN
j S C SLOT (4)
1
7
^ . VALVE
* SPOOL
Figure 8-16—Upper End View of
Rotary Valve - Left Turn
.0004 in. smaller than the inside
diameter of the valve body. This
close fit allows very little, if any,
oil flow between the two surfaces.
The valve spool has four holes
drilled near the upper end of it
which are in line with the four re-
turn slots in the valve body. These
holes allow oil to flow from the
return slots in the valve body to
the center of the spool and on to
return port in the housing. The
outside diameter of the spool has
eight slots machined on it, four
are for opening the right turn
holes in the valve body to the
pressure slots or to the return
slots in the valve body. The other
four slots on the spool serve the
same function for the left turn
holes in the valve body.
Basically the rotary valve as-
sembly is divided into two sepa-
rate assemblies which are fasten-
ed together by the torsion bar. To
completely understand how the
rotary valve functions, it must be
known what parts are firmly at-
tached together. Starting with the
stub shaft which is fastened to the
steering wheel through the upper
steering shaft, the first assembly
consists of the stub shaft, valve
spool and upper end of the torsion
bar. A pin on the outside diameter
of the stub shaft retains the valve
spool to it and a pin at the upper
end of the stub shaft attaches the
upper end of the torsion bar and
shaft together. See Figure 8-17.
The other assembly which is con-
nected to the front wheels of the
car through linkage, pitman shaft
and rack-piston nut, consists of
the worm, valve body, valve body
cap and lower end of the torsion
bar.
The worm is attached to the valve
body by a pin located at the upper
end of the worm. A pin on the in-
side diameter of the valve body
fastens the valve body cap to the
valve body. To complete this as-
sembly, a pin attaches the valve
body cap to the lower end of the
torsion bar.