NEUTRAL WITH ENGINE RUNNINGWhen the engine is started with the console selectionlever in the NEUTRAL position, the oil pump (15) pulls oilfrom the reservoir (18) through the magnetic strainer (16)and sends the oil to the filter (13). Oil from the filter issent to the selector valve (19) and to the pressure controlvalve (1).With the spool (14) for direction selection in theNEUTRAL position, the passage to the direction clutchesis not open to the flow of oil.Some of the oil from the oil pump is sent to thepressure control valve (1). The oil with pressure goesinto the inlet ratio valve (5) through an orifice and worksbetween the slug and the ratio valve to move the ratiovalve to the right and close the passage to the reservoir.Pressure oil also goes through a passage and adrilled hole in the modulation relief valve (2) and to theleft end of differential and safety valve (6). The pressureoil in the drilled hole in the modulation relief valve (2)also opens a poppet valve and works between the slugand the modulation relief valve (2).When the pressure of the oil gets to approximately75psi (5.3 kg/cm2) (517 kPa), the pressure oil betweenthe slug and the modulation relief valve moves the valveto the right and connects passages to send oil to thetorque converter (4).This pressure oil also moves differential and safetyvalve (6) to the right just far enough to open the oilchamber at the left end of the differential and safetyvalve to the reservoir through the body of selector valve(19). In this position, the oil chamber for load piston (3)is connected to a passage to the reservoir.Because no pressure oil is in the chamber for loadpiston (3), the oil pressure can not go over approximately75 psi (5.3 kg/cm2) (517 kPa). This oil pressure isprimary pressure.With the console selection lever in the NEUTRALposition, all the clutches are open to the reservoir andthey can not engage. Because no speed or no directionclutches are engaged, the machine will not move.If the engine is started with the console selectionlever in any position except NEUTRAL, pressure oil issent from selector valve (19) through the orifices indifferential and safety valve (6) to the right side of thevalve. The force of the pressure oil plus the force of thesprings hold differential and safety valve (6) to the left. Inthis position, the direction clutches (No. 1, No. 2 andNo. 3 clutch) can not get pressure oil and will notengage. Because no direction clutch is engaged, themachine will not move.While the console selection lever is in the NEUTRALposition, the pressure oil in the spring side of differentialand safety valve (6) is free to go to the transmissionreservoir through the body of selector valve (19). Thepressure oil on the left side of the combination valve thenworks against the spring force, and differential and safetyvalve moves to a neutral, or balanced position. In thisposition, the direction clutches have no pressure and willnot engage.2-93
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