NEUTRAL WITH ENGINE RUNNING - TM-5-3805-263-14P-2

NEUTRAL WITH ENGINE RUNNING - TM-5-3805-263-14P-2_285

FIRST SPEED FORWARD - TM-5-3805-263-14P-2_287

TM-5-3805-263-14P-2 Grader Heavy Road Motorized Type I Nonsectionalized Type II Sectionalized Manual
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TRANSMISSION HYDRAULIC CONTROLS TM 5-3805-263-14&P-2 NEUTRAL WITH ENGINE RUNNING When the engine is started and the selector valve is in NEUTRAL, oil from the pump goes to main relief valve (4). around relief valve (20), to the selector valve group. Relief valve (20) lets some oil go to cooler (5). Oil from the cooler goes behind the cooler bypass valve (24) and into a cavity for clutch and planetary gear lubrication. At the selector valve group, the flow of oil divides into two separate circuits: signal pressure circuit and system pressure circuit. Signal Pressure Circuit As the engine is started, spring force holds the priority reducing valve (29) so the signal pressure passage to the pilot selector valve (16) is the first circuit to get pressure. As the pressure becomes higher than the spring force, the valve moves to the right and opens the system pressure passage. The valve begins to move when the signal pressure becomes 83 psi (570 kPa). When the signal pressure becomes 96 psi (660 kPa), the valve has moved to the right far enough to not let any more pressure into the signal pressure passage to the pilot selector valve. The pilot selector valve (16) has seven positions. When the control lever is in the NEUTRAL position, the valve sends signal pressure to passages (A) and (F). The function of the signal pressure circuit is to control the movement of the speed selector spools. The signal pressure in passages (A) and (F) moves speed selector spool (35) to the left and speed selector spool (36) to the right. System Pressure Circuit After the pressure becomes 83 psi (570 kPa) in the signal pressure circuit, priority reducing valve (29) opens the passage to the modulating reducing valve (31). The system pressure moves the modu- lating reducing valve (31) to the left until speed clutch pressure (P1) is 90 psi (620 kPa). Since pilot pressure is holding spool (35) and (36) in the positions shown, system pressure goes to the passage for the No. 7 clutch (37) and to the passage for the No. 3 clutch (38). With the speed selector spool (35) held in the position shown by the signal pressure in passage (A), a passage (27) is opened by the speed selector spool (35). This open passage lets pressure oil on the left end of the differential, check, and safety spool (15) go to the reservoir and prevents the spool (15) from moving to the right. Because the differential, check, and safety spool (15) can not move to the right, the direction clutches have no pressure oil and will not engage. If the engine is started in any speed except NEUTRAL, system pressure is sent from the speed selector valve (35) through the orifices in the differential, check, and safety valve (15) to the spring side of the valve (15) holding the valve against its stop. In this position, the direction clutches can not get pressure oil. When the selector lever is moved to the NEUTRAL position, the oil in the spring side of the valve is free to go to the transmission reservoir. The oil pressure on the left side of the valve then works against the spring force and the differential, check, and safety valve (15) moves to the NEUTRAL position. In this position, the direction clutches have no pressure and will not engage. SYSTEMS OPERATION 2-20

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