GMC 1976 ZEO 6083 Maintenance Manual page 538

9- 6 STEERING
Figure 4-Slow Cornering
connected by passage (8) to (9) resulting in a pressure
unbalance on the valve. The flow control valve
moves away from the discharge fitting, but due to the
force of the flow control spring (10) the valve re-
mains closed to the bypass hole (5). The oil pressure
does not build up high enough to cause the pressure
relief valve to actuate, because the oil pump through
the steering gear is allowed to recirculate through the
entire system .
Figure 5-Moderate To High Speed Operation
Moderate To High Speed Operation (Figure 5)
When operating at moderate to high speed, it is
desirable to limit the temperature rise of the oil . This
is done by flow controlling. The control valve in the
steering gear is an open center rotary valve. When
this valve is in the straight ahead position, oil flows
from the pump through the open center valve and
back to the pump reservoir without traveling
through the power cylinder . When this flow exceeds
the predetermined system requirements, oil is
bypassed within the pump . This is accomplished by
the pressure drop which occurs across the flow con-
trol orifice (2). The pressure is reduced at the bottom
of the flow control valve (9) because the orifice (11)
is connected by (8) to the bottom of valve (9).
The pressure unbalance of the valve is sufficient
to overcome the force of the spring (10), allowing the
valve to open the bypass hole (5), and diverting oil
into the intake chamber (6). Supercharging of the
intake chamber occurs under these conditions . Oil at
high velocity discharging past the valve into the in-
take chamber picks up make-up oil at hole (4) from
the reservoir on the jet pump principle. By reduction
of velocity, velocity energy is converted into super-
charge pressure in cavity (6). During this straight
ahead driving conditon, the discharge pressure
should not exceed 100 psi .
Cornering Against Wheel Stops (Figure 6)
When the steering gear control valve is actuated
in either direction to the point of cut-off, the flow of
oil from the pump is blocked. This condition occurs
Figure 6-Pressure Relief