TROUBLESHOOTING THE HMMWV - OD1616 - LESSON 1/TASK 1
drive belt mounted on pulleys attached to the pump shaft and the
engine crankshaft. The power steering system on the HMMWV holds one
quart of Dexron II hydraulic fluid.
(a) The gearbox used in an integral power steering system is
basically a manual gearbox that is adapted to include a power assist
package.
The integral power steering gearboxes are of two types:
offset and inline.
However, since the HMMWV uses the offset or
recirculating ball bearing type of gearbox, that is the only one that
will be discussed in this text. The offset type uses a recirculating
ball-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 with difficulty.
(b) Power Steering Pump. 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 operating. The
pressure and flow relief valves are always built into the pump.
These valves are designed to limit the amount of pressure and flow
the pump develops throughout the different engine speeds. The power
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.
(4) Steering Linkage.
The steering linkage is 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 rod ball studs have
Each tie rod assembly consists of 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.
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