TRANSMISSION THEORY OF OPERATION (CONT)
Oil Flow in Neutral. Oil flows from oil sump through suction screen to charging
pump. Charging pump sends oil through filter to transmission control valve. Oil
enters transmission control valve at main pressure regulator. Oil flows through
orifice in spool of main pressure regulator. As pressure of oil increases, pressure
pushes spool to the right which opens passage to charge torque converter. Spool then
moves as necessary to keep main pressure between 135 to 170 psi.
Pressure of oil used to charge torque converter is controlled by torque converter
pressure regulator. This regulator keeps pressure in torque converter at approxi-
mately 80 psi. Oil from torque converter flows through oil cooler to lubrication
pressure regulator. Lubrication pressure regulator keeps pressure in lubrication
system at 15 to 30 psi. Lubrication system lubricates and cools transmission parts.
Oil flows from main pressure regulator through passages in transmission control
valve to two orifices. Oil flows through one orifice into lubrication system. Oil
flows through second orifice to clutch cutout valve and then to shifting spool.
Oil enters detent area of shifting spool and flows to area near center of shifting
spool where oil is available for low clutch, high clutch, and for operation of trim-
mer plug. With shifting spool in neutral, all clutch circuits are connected to oil
Trimmer plug controls main pressure as a clutch begins to engage. Normally, main
pressure holds trimmer plug to the left, compressing spring. While trimmer plug is
compressing spring, main pressure is kept near maximum pressure.