TRANSMISSION HYDRAULIC CONTROLSSYSTEMS OPERATIONTM 5-3805-263-14&P-2NEUTRAL WITH ENGINE OFFWith the engine off, the pump is not beingturned and there is no pressure oil in the system.With no pressure oil, the two position selectorspools (17), (18), and (36) and the load piston (32)are held by spring force against their respectivestops. The three position selector spool (35) is heldin its center position by spring force.The selector valve group has three manuallyoperated spools: pilot selector spool (16), directionselector spool (28), and manual modulation spool(14). All of the other spools are operated by pilotpressure. The pilot selector spool (16) sends pilotpressure oil to the speed selector spools which inturn send pressure oil to the speed clutches. Thedirection selector spool (28) sends oil to thedirection clutches. The manual modulation spool(14) gives a control for the P2 pressure to thedirection clutches. Make reference to MANUALMODULATION VALVE.The main relief valve (4) has a relief valve (20)for maximum system pressure, an oil cooler bypassvalve (24) for the oil cooler, and a lubrication reliefvalve (25) for maximum pressure of the clutch andplanetary lubrication oil. Relief valve (20) keepsthe system pressure from getting too high. Bypassvalve (24) prevents the pressure in the oil coolerfrom getting too high. Relief valve (25) keeps thelubrication oil for the speed clutches and theplanetary gears from getting too high.2-18
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