GMC 1990 Light Truck Repair Manual page 115

SUBJECT
Description ........................................................................................................................
Saginaw Integral Power Steering Gear— RV, G, P, ST, M ..................................
Disassembly ...................................................................................................................
Cleaning and Inspection ............................................................................................
Assembly ........................................................................................................................
Saginaw Integral Power Steering Gear— CK (GMT 400) .......................................
Saginaw Power Steering Pump— Model TC .............................................................
Disassembly ...................................................................................................................
Cleaning and Inspection ............................................................................................
Assembly ........................................................................................................................
Saginaw Power Steering Pump Model P ...................................................................
Disassembly ...................................................................................................................
Cleaning and Inspection ............................................................................................
Assembly ........................................................................................................................ .
Specifications ....................................................................................................................
Special Tools ....................................................................................................................
DESCRIPTION
The hydraulic power steering system consists of a
pump, an oil reservoir, a steering gear, a pressure
hose, and a return hose.
The steering gear is made by Saginaw Division, Gen­
eral Motors. The steering gear is identified by a large S
cast into the side of the housing. A building date is
stamped in the cover. The building date is a four digit
number. The first three digits are the Julian day of the
year. The remaining digit is the last digit of the year.
The power steering pump is made by Saginaw Divi­
sion, General Motors.
The power steering gear (figure 1) has a recirculating
ball system which acts as a rolling thread between the
wormshaft and the rack piston. The wormshaft is sup­
ported by a thrust bearing preload and two conical
thrust races at the lower end, and a bearing assembly
in the adjuster plug at the upper end. When the worm­
shaft is turned right, the rack piston moves up in gear.
Turning the wormshaft left moves the rack piston down
in gear. The rack piston teeth mesh with the sector,
which is part of the pitman shaft. Turning the worm­
shaft turns the pitman shaft, which turns the wheels
through the steering linkage.
The control valve in the steering gear directs the
power steering fluid to either side of the rack piston.
The rack piston converts the hydraulic pressure into a
mechanical force. If the steering system becomes dam­
aged and loses hydraulic pressure, the vehicle can be
controlled manually.
The hydraulic pump is a vane-type design. There are
two types, submerged and nonsubmerged. Submerged
pump (P models) have a housing and internal parts
that are inside the reservoir and operate submerged in
SECTION 3B3
POWER STEERING
CONTENTS
POWER STEERING 3B3-1
fluid. The nonsubmerged pump (TC models with or
without reservoir) function the same as the submerged
pump except that the reservoir is separate from the
housing and internal parts.
There are two bore openings at the rear of the pump
housing. The larger opening contains the cam ring,
pressure plate, thrust plate, rotor and vane assembly,
and end plate. The smaller opening contains the pres­
sure line union, flow control valve, and spring. The flow
control orifice is part of the pressure line union. The
pressure relief valve inside the flow control valve limits
the pump pressure.
SAGINAW INTEGRAL
POWER STEERING
GEAR—RV, G, ST, M
NOTICE: Repair the steering gear In a clean,
dust-free location, using clean tools and equip­
ment. Dirt or grit will damage the machined
surfaces and result in leakage or damage to
the steering gear assembly.
If broken components or foreign materials are found
during disassembly of the gear the hydraulic system
should be disassembled, inspected, cleaned and
flushed before servicing is complete.
The ball nut and control rings (seals) generally need
not be replaced unless cut or damaged. If cut or dam­
aged, inspect all mating parts for burrs, cracks,
scratches, or damage. Replace or repair as needed.
In some instances, ''power steering fluid" will be
specified to lubricate parts upon assembly. In these
cases, GM Power Steering Fluid, part no. 1050017 or
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