TRANSMISSION HYDRAULIC CONTROLS
SYSTEMS OPERATION
TM 5-3805-263-14&P-2
NEUTRAL WITH ENGINE OFF
With the engine off, the pump is not being
turned and there is no pressure oil in the system.
With no pressure oil, the two position selector
spools (17), (18), and (36) and the load piston (32)
are held by spring force against their respective
stops. The three position selector spool (35) is held
in its center position by spring force.
The selector valve group has three manually
operated spools: pilot selector spool (16), direction
selector spool (28), and manual modulation spool
(14). All of the other spools are operated by pilot
pressure. The pilot selector spool (16) sends pilot
pressure oil to the speed selector spools which in
turn send pressure oil to the speed clutches. The
direction selector spool (28) sends oil to the
direction clutches. The manual modulation spool
(14) gives a control for the P2 pressure to the
direction clutches. Make reference to MANUAL
MODULATION VALVE.
The main relief valve (4) has a relief valve (20)
for maximum system pressure, an oil cooler bypass
valve (24) for the oil cooler, and a lubrication relief
valve (25) for maximum pressure of the clutch and
planetary lubrication oil. Relief valve (20) keeps
the system pressure from getting too high. Bypass
valve (24) prevents the pressure in the oil cooler
from getting too high. Relief valve (25) keeps the
lubrication oil for the speed clutches and the
planetary gears from getting too high.
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