POWER STEERING SYSTEM
SECTION X
their sealing contact against the ring during normal opera-
MINIMUM HACKLASH ADJUSTMENT. Adjust the back
tion.
lash so that a very slight drag is felt through the mid-
position high spot while turning the steering wheel slowly
Maximum pump delivery and maximum system pressure are
from one extreme position to the other.
determined by the integral flow control and relief valve in
the outlet cover. The flow control and relief valve is shown
Backlash of the studs in the the groove up as backlash at
schematically in Figure 10-9.
the steering wheel and at the ball on the steering arm. The
groove is purposely cut shallower, and narrower, in the
An orifice in the cover limits maximum flow. A pilot-
mid-position range of travel of each stud to provide close
operated type relief valve shifts to divert excess fluid de-
adjustment where usually the straight-ahead-driving action
livery to tank, thus limiting the system pressure to a pre-
takes place. It also makes this close adjustment possible
scribed maximum.
after normal wear occurs without causing a bind elsewhere.
Figure 10-9, Part A, shows the condition of the valve com-
Adjust through the mid-position. Do not adjust in positions
ponents when the total pump delivery can pass through the
off mid-position as backlash at these points is normal and
orifice. This condition usually occurs only at low drive
not objectionable. To adjust proceed as follows:
speeds. The large spring chamber is connected to the pres-
sure port through an orifice. Pressure in this chamber
1. Tighten the side cover adjusting screw until the adjust-
equalizes pressure at the other end of the relief valve spool
ment is correct.
and the light spring holds the spool dosed. Pump delivery is
2. Tighten the locknut.
blocked from the tank port by the spool land.
3. Give the gear a final test.
When pump delivery is more than the flow rate determined
by the orifice plug, a pressure build-up forces the spool
open against the light spring. Excess fluid is throttled past
HYDRAULIC PUMPS
the spool to the tank port as shown in Part 8.
HYDRAULIC PUMP (37Z135,37Z182,37Z196)
If the pressure in the system builds up to the relief setting
GENERAL. The hydraulic pump supplies fluid to the
(Part C), the pilot poppet is forced of! its seat. Fluid in the
power steering and outrigger systems. The pump is
large spring chamber flows through the spool and out to
mounted on the upper rear of a G.M. engine and on top of
tank. This flow causes a pressure differential on the spool,
the hydraulic pump drive assembly when Cummins engines
shifting it against the light spring. All pump delivery is thus
are used.
permitted to flow to tank.
A cutaway view of a hydraulic pump is shown in Figure
REMOVAL-ENGINE MOUNTED. To remove an engine
10-7. The major components of the pump are a ported
mounted power steering pump, proceed as follows:
body and cover. a driveshaft, a pumping cartridge, and a
1. Remove all dirt from the pump and connections with a
pressure plate. The components of the pumping cartridge
suitable cleaning solvent.
are an elliptical ring, a slotted rotor which is splined to the
driveshaft, and twelve vanes fitted into the rotor slots.
2. Mark the hose connections to assure proper connection
upon reassembly.
The differences between these power steering pumps is the
GPM rating and the direction of rotation.
3. Remove the hydraulic hoses from the pump.
OPERATION. Fluid enters the pumping cartridge through
4. Plug the ports of the pump and cap-all lines to prevent
the inlet port in the body and is discharged through the
the entry of dirt into the system.
pressure plate to the outlet port in the cover. The action of
a pumping cartridge is shown in Figure 10-8.
5. Remove the mounting bolts and pull the pump away
from the engine.
As the rotor turns, centrifugal force on the vanes causes
them to follow the elliptical inner surface of the ring.
REMOVAL - PUMP DRIVE MOUNTED. To remove a
Radial movement of the vanes and turning of the motor
power steering pump mounted on the pump drive, proceed
causes the chamber between the vanes to increase as the
as follows:
vanes pass the inlet sections of the ring. This results in a low
1. Remove all dirt from the pump and connections with a
pressure condition which allows atmospheric pressure to
suitable cleaning solvent.
force fluid into the chambers. This fluid is trapped between
the vanes and carried past the large diameter or dwell sec-
2. Mark the hose connections to assure proper connection
tion of the ring. As the outlet section is approached, the
upon reassembly.
ring diameter decreases and the fluid is forced out into the
system. System pressure is fed under the vanes, assuring
3. Remove the hydraulic hoses from the pump.
10-8
