TM-9-2520-234-35 Technical Manual for M109 Transmission XTG-411-2A Download

PAR 30 DESCRIPTION AND OPERATION OF CHAP 2, SEC IV RIGHT- AND LEFT-OUTPUT DRIVE ASSEMBLIES top land. Pressure in this cavity pushes the valve downward against a spring at its lower end. As the valve moves downward, it uncovers a port which admits oil to the lockup shift valve bore. When the lockup shift valve is held upward by its spring, the oil flows unrestricted to the torque con- verter and keeps it charged. When the valve is in the downward position, flow to the converter is limited by an orifice. Another passage is blocked by the middle land of the lockup shift valve. c. Oil entering the main-pressure regulator bore at the lower connection flows into a cavity between the two larger lower lands of tine valve. If the oil is cold or the speed of the pump is sufficient, the oil flow may exceed the capacity of the converter. The pressure then rises and causes the valve to move downward, un- covering a port through which part of the flow exhausts to the sump. d. Main-pressure regulation in neu- tral (converter operation) is maintained only by the compression of the springs at the lower end of the valve. Should engine speed be increased sufficiently to cause lockup (increased pitot pressure forces the lockup shift valve downward), main pres- sure would flow to the lockup clutch. At the same time, a branch from the lockup clutch line directs pressure to the area between the top of the lockup shift valve and the bottom of the high knockdown plug. Thus, in neutral lockup, main pres- sure is lowered because more oil is allowed to escape into the converter feed line (and, in some instances, to the sump). e. At the lockup cutoff valve, oil is directed to two points. One point is the right end of the valve. The other is through an orifice (earlier models; later models have no orifice) to a passage which feeds the manual selector valve. When no shifts are being made, the lockup cutoff valve remains in the position shown. From the lockup cutoff valve, main pressure is directed to the manual selector valve. This valve is in neutral position and does not direct pressure to any of the range clutches. It does, however, direct pressure to the first, neutral and reverse 1 signal line (through the hollow center of the valve). Pressure in the signal line pushes the drive clutch relay valve upward against its stop, alining the hydraulic cir- cuit for drive by means of the geared steer clutches. f. At the throttle and throttle regu- lator valves, main pressure is supplied to two points. The left connection is blocked at closed throttle. When the throttle is opened, the throttle valve lever moves the throttle valve to the left. The spring be- tween the throttle valve and throttle regu- lator valve transmits this movement to the throttle regulator valve. When the throttle regulator valve moves to the left, a port is uncovered, allowing oil to flow to the TV line. A branch of the TV line directs oil, through an orifice, to the left end of the throttle regulator valve where it exerts sufficient pressure to balance the compression of the TV spring and regulate TV pressure. Thus, the greater the move- ment of the throttle valve to the left, the greater is the compression of the TV spring and, consequently, the greater the pressure in the TV line. TV pressure is directed to the 10 lower side of the lockup shift valve, where it inhibits the initial downward movement of the valve. g. When the lockup shift valve moves downward against TV pressure far enough to close the TV pressure passage, it no longer is opposed by TV pressure (except at full throttle, h , below) and rapidly com- pletes its downward stroke. The cavity below the valve exhausts through the T pressure line and an orifice shown above the throttle valve. h. When the throttle is completely open, the throttle valve moves far enough to the left to uncover the T pressure port. Change 2 27