TM 5-3805-260-24NEUTRAL WITH ENGINE NOT RUNNINGThe basic components of the oil system for thehydraulic controls are: oil reservoir ( 18), magneticstrainer (16), oil filter (13), oil pump (15), pressure controlvalve (1), selector valve (19), torque converter (4),lubrication relief valve (8) and oil cooler (7). All the oilpassages are inside the cases except the supply lines forthe oil pumps and the lines to and from the oil cooler.The hydraulic controls have a pressure control valve(I) and a selector valve (19). The controls are fastenedto the clutch housings and are completely inside thetransmission case.Valve spools (20) in the selector valve are connectedtogether and work as a unit. These spools send oil tothe speed clutches (No. I, No. 4, No. 5 or No. 6clutch). Valve spool (14) in the selector valve sends oilto the direction clutches (No. 2 or No. 3 clutch). Onespeed clutch (No. 1, No. 4, No. 5 or No. 6 clutch) andone direction clutch (No. 2 or No. 3 clutch) must beengaged to make the machine move.The differential and safety valve (6) is in the pressurecontrol valve. This valve causes a difference in pressurein the speed and direction clutches, keeps the machinefrom moving if the engine is started in any speed exceptNEUTRAL, controls the flow of oil to the directionclutches, and is a check valve for the chamber behindload piston (3).With the engine not running, the pump is not beingturned and there is no pressure oil in the system. Thesprings for valves (2) and (6) and load piston (3) areextended and the valves and load piston are against theirstops.This chart gives a description of the function of thevalves in the hydraulic controls.VALVEFUNCTIONControls the increase of pressure in the direction and speedModulation Relief Valve (2)clutches to gradually engage the clutches.and Load Piston (3).Does not let the system pressure be more than 310 psi (21.80 kg/cm2) (2137 kPa).Ratio Valve (5).Does not let the oil going to the torque converter have apressure of more than 115 psi (8.08 kg/cm2) (793 kPa)Controls the pressure difference between the speed and direction clutches.Keeps oil from going to the direction clutches if the machine isDifferential and Safety Valve (6).started in any speed except NEUTRALControls the flow of oil to the direction clutches.Opens a return passage to release the pressure from the right end ofthe load piston during a shift.Direction Selector Spool (14).Opens the direction clutches to pressure oil or to the reservoir.Speed Selector Spools (20)Opens the speed clutches to pressure oil or to the reservoir.2-91
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