Rack-Piston And Worm Assembly-To Assemble; Piston Ball Sizes - Rolls-Royce Silver Shadow Workshop Manual

Rolls-Royce Silver Shadow & Bentley T Series
Workshop Manual
4. Inspect the rack-piston and end plug to ensure
the pre-load of the worm and rack-piston ball as-
that the threads are not damaged.
sembly proceed as follows.
''
Inspect the rack-~iston teeth and rack-~istOn
7 Clamp the rack-piston in
a
suitably protected
outside diameter for abnormal wear, scoring or burrs.
with the worm shaft pointing upwards.
Do not
6. Examine the piston ring; if damaged, remove
distort the rack-piston by over-tightening the vice.
and discard the ring and backing ' 0 ' ring seal.
8. Place the valve assembly on the worm shaft,
engaging the worm shaft drive pin. Rotate the worm
shaft until it extends 1.25 in. (3,17 cm.) from the rack-
Rack-piston and worm assembly-
piston to the thrust bearing face. This is the centre
To assemble
position.
d
1. Thoroughly clean the parts and lubricate them
9. Apply a torque wrench with
3
in. (19,05 mm.)
t3
with the approved power steering fluid.
a
socket to the stub shaft and rotate the wrench several
d
2. Lubricate the new backing ' 0 ' ring seal and
times through an arc of approximately 60" in both
insert it in the piston ring groove on the rack-piston.
directions then take a torque reading. The highest
M
Do not allow the seal to become twisted. Fit the new
average reading obtained with the worm rotating
w
piston ring into the groove over the
'0'
ring seal.
should be between 1 lb. in. apd 4 lb. in. (0,012 kg.m.
E
.-
-U
3. Insert the worm into the end of the rack-piston,
and 0,046 kg.m.).
d
If
the reading is below 1 lb. in. (0,012 kg.m.) a new
C
.
-
from the end opposite the piston ring, until the worm
&
is against the rack-piston shoulder.
set of balls must be fitted. Service replacement balls
are available in sizes listed in the following chart.
3. Load 16 balls into the guide hole nearest to the
piston ring while rotating the worm anti-clockwise to
feed the balls through the circuit. Alternate black
balls with white balls throughout the circuit.
5. Apply a liberal amount of petroleum jelly to one
ball return guide and load the remaining 6 balls into
the guide. Place the outer guide over the balls and
ball guide and insert the guides into the guide holes of
03
rg
the rack-piston. Ensure that black ball in the guide is
52
installed next to the white ball in the rack-piston. The
C
$
guides should fit loosely.
-
6 . Place the return guide clamp over the guides and
a
secure it with two screws and lockwashers; torque
tighten to 12 lb. ft. (1,66 kg.m.).
The worm groove is ground with a high point in the
centre. When the rack-piston passes over this high
point a load of between 1 lb. in. and 4 lb. in. (0,12
kg.m. and 0,46 kg.m.) should be obtained. To measure
Note the ball size stamped on the rack-piston and
fit the next size larger balls to increase the pre-load.
Note If a number cannot be found on the rack-
piston, the original ball size was 7.
A change of one ball size (higher size code) will
increase the pre-load approximately 1 lb. in. (0,012
kg.m.). Final pre-load on replacement balls should
be between 2 lb. in. and 3 lb. in. (0,023 kg.m. and
0,035 kg.m.).
10. Remove the valve assembly from the worm.
11.
Remove the rack-piston from the vice.
12. Insert the rack-piston arbor until it registers
against the worm shaft and turn the rack-piston on to
the arbor. Do not allow the arbor to separate from
the worm shaft until the rack-piston is fully on the
arbor.
Piston ball sizes
SIZE RANGE OF BALL
0281204.28130 in. (0,71425 cm.-O,71450 cm.)
0.28128-0.28138 in. (0,71427 cm.-0,71452 cm.)
0 . 2 8 1 36428146 in. ( 0 , 7 1 4 5 1 cm.-0,71490 cm.)
0.28144428154 in. (0,71485 cm.-0,71511 cm.)
SIZE CODE
7
8
9
1 0
MEAN DIA.
0.28125 in. (0,71437 cm.)
0.28133 in. (0,71457 cm.)
0 . 2 8 1 4 1 in. (0,71486 cm.)
0.28149 in. (0,71498 cm.)