INTRODUCTION TO THE HMMWV - OD1615 - LESSON 3/TASK 1
type gearbox with a rack above or on the opposite side of the ball nut. The
power steering force is developed in the power piston, which is offset from
the worm and nut and attached to the rack. The power steering gear on the
HMMWV uses a steel ball bearing within the gear to act as a rolling thread.
With this type of gearbox, should a complete power steering system failure
occur, the vehicle can still be steered manually, though with difficulty.
All power steering systems contain a pump that supplies hydraulic fluid
under pressure to the other components in the system. The pump, which may
be of the gear teeth, rotor, or vane type, is usually driven by the engine
by means of a V-belt.
The pump is functional whenever the engine is
These valves are designed to limit the amount of pressure and flow
the pump develops throughout the different engine speeds.
steering pump on the HMMWV is a Saginaw 125, with a maximum output of 1450
psi and a maximum flow rate of 3.5 gallons per minute.
e. Steering Linkage. The steering linkage is of a parallelogram design
that is sometimes referred to as the Ackerman system or articulated linkage.
The steering linkage consists of two adjustable tie rod assemblies, a center
link, pitman arm, and an idler arm. All components are connected by spring-
loaded nonadjustable ball studs.
Only the idler arm, pitman arm, and tie
a tie rod, tie rod end, adjusting tube and clamps.
The threaded tube
connects the tie rod and tie rod ends, which have left and right hand
threads to allow for toe adjustment.
The parallelogram steering linkage is a very popular steering system for
independent front suspension and is used on many of today's vehicles.
(1) Centerlink. The parallelogram steering system uses a centerlink,
otherwise known as an intermediate rod or track rod, to connect the steering
arms together. The turning action of the steering box is transmitted to the
centerlink through the pitman arm. The pitman arm also provides support for
the centerlink. The two components are connected by a hinge or ball joint.
The pitman arm is the component that transfers