Chevrolet 10 1971 Series Chassis Service Manual page 360

STEERING 9-20
3. Install ball stud nuts and torque to specifications.
Continue to tighten nuts enough to align castellations
General Description ...................................................................................9-20
Maintenance and Adjustments .............................................................. 9-20
Adjustments ......................................................................................... 9-20
Power Steering Gear ................................................................. ... . 9-20
Pump Belt Tension ........................................................................ 9-20
Fluid Level .............................................................................................9-21
Two variations of integral power steering are used in
the 10-30 series trucks; "constant ratio" ("P" Models)
and "Variable Ratio" ("C-K" Models).
The power steering gears are of the same general de­
sign and are overhauled in a like manner. Both gears
incorporate the recirculating ball system in which steel
balls act as a rolling thread between the steering worm­
shaft and rack-piston. The rack-piston nut is geared to
the sector of the pitman shaft. The valve is contained in
the gear housing thus eliminating the need for separately
mounted valve and cylinder assemblies.
Variable ratio steering is faster nearer the corners,
requiring fewer turns of the steering wheel to move the
front wheels from stop to stop, while steering effort is
not increased. It also provides more precise control and
better response in maneuvering, particularly in sharp
rapid turns and in parking.
Variable ratio steering is accomplished by a pitman
shaft sector incorporating a short tooth on either side of
a long center tooth, rather than a sector with three teeth
of equal length as in the constant ratio gear (fig. 37).
Companion changes are also made in the rack-piston
teeth.
Hydraulic pressure is provided by an engine-driven
vane-type pump which is bracket mounted to the left side
ADJUSTMENTS
Power Steering Gear
The over-center adjustment (fig. 38) is the only power
steering gear adjustment which can be made on the car.
However, in order to make this adjustment, it is also
necessary to check the combined ball and thrust bearing
preload.
1. Remove the pitman shaft nut. Mark the relation of
the pitman arm to the pitman shaft. Disconnect the
pitman arm from the pitman shaft using Puller Tool
J-6632 (fig. 1).
2. Loosen the pitman shaft adjusting screw locknut and
thread the adjusting screw out to the limit of its
travel through the side cover.
3. Disconnect the battery ground cable.
4. Remove the horn button.
5. Turn the steering wheel through its full travel, then
POWER STEERING
Page
GENERAL DESCRIPTION
M AINTENANCE A N D ADJUSTMENTS
with holes in studs.
4. Install cotter pins and lubricate.
INDEX
Bleeding Hydraulic S y s t e m ................................................................. 9-21
Hydraulic System Checks
Component Replacement and Repairs
Power Steering Gear
Power Steering Pump
Power Steering Hoses
PITMAN SHAFT SECTOR
CONSTANT RATIO
Fig. 37— Pitman Shaft Sector Teeth
of the engine. Pressure is delivered from the pump through
two hoses to the variable ratio steering gear.
locate the wheel at its center of travel.
6. Check the combined ball and thrust bearing preload
with an inch-pound torque wrench on the steering
shaft nut by rotating through the center of travel
(approximately 1/4 turn in each direction). Note the
highest reading.
7. Tighten the pitman shaft adjusting screw and check
torque at steering shaft nut until over-center preload
and total steering gear preload falls within specifi­
cations. Refer to torque specifications at rear of
manual for correct torque values.
8. Install horn button and connect the battery ground
cable.
9. Connect the pitman arm to the pitman shaft, lining up
the marks made at removal.
The pitman arm to pitman shaft fastener
NOTE:
is an important attaching part in that it could
affect the performance of vital components and
................................................................. 9-21
................................................ 9-22
........................................................................9-22
....................................................................... 9-23
........................................................................ 9-23
RACK PISTON
VARIABLE RATIO
10-30 CHEVROLET TRUCK SERVICE MANUAL
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