TM 5-3805-264-14&P
1-17.
HYDRAULIC SYSTEM.
a.
The hydraulic system powers the hydraulic cylinder, which raises and lowers the dump body
b.
Major components of the hydraulic system are:
(1)
Hydraulic Pump.
(a)
The gear pump is mounted directly to the vehicle PTO. It supplies the system with a
working pressure of 2500 psi (17,238 kPa) with approximately 1200 rpm input speed from the PTO.
(b)
There is one port at the rear of the pump. It is connected to the bottom of the reservoir
and receives, through a suction hose. hydraulic fluid from the reservoir.
(2)
Control Valve.
(a)
The control valve is an integral part of the hydraulic pump. It is a single spool type with
the control spool linked mechanically to the hydraulic control lever in the cab.
(b)
When the hydraulic control lever is pulled back, the control valve routes hydraulic fluid
through port B to the hydraulic cylinder. This extends the cylinder and raises the dump body.
(c)
When the hydraulic control lever is pushed forward, the control valve routes hydraulic
fluid through port A to the hydraulic cylinder. This retracts the hydraulic cylinder and lowers the dump body.
(d)
A third control valve port returns hydraulic fluid through the filter and into the reservoir.
(e)
The control valve has a relief valve which is set at 2500 psi (17,238 kPa).
(3)
Hydraulic Cylinder.
(a) The hydraulic cylinder is a three-stage telescoping cylinder with a 124 in. (315 cm)
stroke.
frame.
(b)
The bottom of the hydraulic cylinder is attached by a pivot pin to the cylinder support
(c)
The collar of the hydraulic cylinder is attached by pivot pins to the dump body inside
the long beam at the front of the dump body.
(d)
The pivot pins at the top and bottom of the cylinder allow the cylinder to pivot as it is
extended and retracted. Composite lubrication-free bearings at these pivot points ensure smooth, maintenance-
free operation.
(4)
Hydraulic Filter.
(a)
The filter is located on top of the reservoir. It filters hydraulic fluid as it returns to the
reservoir through the return line from the control valve.
(b) The filter element is made of lo-micron synthetic material. A filter service indicator
gage indicates when the filter needs replacing.
(c)
The filter has a by-pass feature.
(5)
Hydraulic Reservoir.
(a)
The reservoir is an all steel container with a 12.75 gal. (48.21) capacity.
(b)
It is mounted upright, bolted to the hydraulic cylinder mount, between the hydraulic
cylinder and the vehicle cab.
(c)
The fill cap is also a breather and a strainer. It must be kept clean at all times.
1-16
