GMC 1989 Light Duty Truck, Repair Manual, Page: 116 / 998

3B3-2 POWER STEERING
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, General
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 1989 Interim design will be marked with a X after the
build number. This signifies the change in the pitman shaft
seal arrangement.
The power steering pump is made by Saginaw Division,
General Motors.
The power steering gear (figure 1) has a recirculating ball
system which acts as a rolling thread between the worm ­
shaft and the rack piston. The worm shaft is supported by a
thrust bearing preload and two conical thrust races at the
lower end, and a bearing assem bly in the adjuster plug at
the upper end. When the worm shaft is turned right, the rack
piston moves up in gear. Turning the worm shaft 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 w orm shaft turns the pitm an shaft, w hich 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. Subm erged pump
(P models) have a housing and internal parts that are inside
the reservoir and operate subm erged in oil. The nonsub­
merged pump (TC models with or w ithout reservoir) func­
tion the same as the subm erged pum p 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, pres­
sure plate, thrust plate, rotor and vane assem bly, and end
plate. The sm aller opening contains the pressure line
union, flow control valve, and spring. The flow control ori­
fice is part of the pressure line union. The pressure relief
valve inside the flow control valve limits the pum p pressure.
SAGINAW INTEGRAL POWER STEERING GEAR—
RV, G, P, ST, M
NO TIC E: R e p a ir the s te e rin g g e a r in a clean, d ust-
free lo catio n, using c lean tools a n d e q u ip m e n t.
D irt o r g rit w ill d am ag e the m a c h in e d surfaces
an d resu lt in leakag e o r d am ag e to the s teerin g
g e a r assem bly.
If broken com ponents or foreign m aterials are found dur­
ing disassembly of the gear the hydraulic system should be
disassembled, inspected, cleaned and flushed before serv­
icing is complete.
The ball nut and control rings (seals) generally need not
be replaced unless cut or dam aged. If cut or damaged,
inspect all mating parts for burrs, cracks, scratches, or
damage. Replace or repair as needed.
In some instances, “ power steering flu id ” will be speci­
fied to lubricate parts upon assembly. In these cases, GM
Power Steering Fluid, part no. 1050017 or equivalent
should be used. DO NOT use brake fluid, automatic trans­
mission fluid, or other non-approved fluids.
DISASSEMBLY
0
Remove or Disconnect (Figures 1 through 11)
Tools Required:
J 4245 Internal Snap Ring Pliers
J 21552 Ball Retainer Tool
J 8524-1 Bearing Remover
J 7624 Spanner W rench
J 7079-2 Driver
J 6278 Pitman Shaft Bearing Puller
J 21552 Rack Piston Arbor
1. Retaining Ring (220) (figure 2).
• Pry retaining ring out of the housing groove with
a screwdriver (figure 3).
2. Plug (219). Turn stud shaft (251) to the left only until
the plug is forced out of the cylinder.
3. Seal (218).
4. Plug (215) from the rack piston (214) (figure 4).
5. Bolt (226).
6. Sector shaft assem bly (221, 222, 225, 227).
7. 1989 Interim: Dust Seal (253) (figure 1).
8. Retainng ring (205) with J 4245.
9. W ashers (207) and seals (208) using a screwdriver.
• 1989 Interim: W asher (207) and seal (254)
(figure 1).
10. Bearing (209). If necessary, use tool J 6278 (figure 5).
11. Rack piston (214) and balls (213).
• Insert tool J 21552 into the rack piston bore with
the pilot of the tool seated into the end of the
worm (248).
• Hold the tool against the worm and turn the stub
shaft to the left. The rack piston (214) will be
forced onto the tool.
• Hold the tool and pull the rack piston toward the
handle until it is against the flange on the tool.
This will prevent the end circuit balls from falling
out.
12. Adjuster nut (245).
13. Adjuster plug (240) using J 7624 (figure 6).
• Retaining ring (244) using J 4245.
• W asher (243), seal (242) and bearing (241).
• Bearing retainer (234). Pry the retainer with a
t screw driver at the raised area (figure 7).