C3, TM 9-2320-211-20
Section XXXIX. MAINTENANCE OF WRECKER CRANE
M543 AND M543A1
2-292. General.
b. Adjustment.
a. The M543 and M543A1 wrecker crane models are
hydraulically operated units powered by the vehicle's
engine. An extendable boom on both models is capable of
required to stop oil seepage. When the adjustment has
360 rotation (270 with stops) and approximately 45
been used up, a new packing must be installed.
elevation. These models include a hydraulic crane, winch
(2) When adjusting the packing nut on a boom
assembly, and power train assembly.
cylinder, remove the block (fig. 2-257), and extend the
b. Each of the crane's functions is dependent upon
boom slowly until the adjustment opening in the inner
hydraulic pressure supplied by a valve type hydraulic
boom at the cylinder packing nut is alined with the stop
pump. This pump forces pressurized fluid through a
block opening in the outer boom.
swivel valve to each of the crane's hydraulic components.
(3) Adjust the packing nut using a punch, or bar, to
Control of the crane is accomplished by a single unit
tighten it. Tighten it only as much as is required to stop
control valve bank assembly. The valve assembly controls
the oil seepage.
all of the crane's functions, such as lifting or lowering the
boom, winding or unwinding the hoist drum, extending
a. General. The hydraulic system operates at
or retracting the boom, and swinging the boom left or
approximately 1,200 psi. An adjustable relief valve in the
right. On later vehicles the hydraulic system is equipped
control valve bank governs this pressure and protects the
with a filter. An indicator on the outside of the filter
hydraulic system from going beyond 1,210 to 1,215 psi.
indicates the filter element condition and determines the
b. Relief Valve Test.
necessity of cleaning.
(1) Remove pipe plug from the control valve bank,
and install hydraulic pressure gage (2, fig. 2-4) as shown
removal and installation.
(2) Lower hoist cable to the ground to prevent
fouling of the hoist cable block with the boom sheaves
a. General. The two boom elevating cylinders and the
while testing the relief valve setting.
boom crowd cylinder have an adjustable packing gland
(3) With boom fully extended, move control lever to
nut (fig. 2-251) to correct oil leakage at the packing
the extended position, and hold it there.
around the piston rod. Adjustment is the same for all
(4) While holding control lever in the extended
three cylinders.
position, observe pressure indicated on hydraulic
(5) The pressure indicated on gage is pressure at
which the relief valve is opening. If gage indicates an
incorrect relief valve setting (more or less than 1,210 to
1,215 psi) adjust relief valve as described in c below.
c. Relief Valve Adjustment. Gar Wood Valve Bank
Assembly, 10876206.
(2) Turn adjusting screw as required to obtain
correct relief valve setting of 1,210 to 1,215 psi.
