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

PAR 34-37 OPERATION OF HYDRAULIC SYSTEMS CHAP 2, SEC IV d. In fourth gear, main pressure is di- rected to the top of the high knockdown plug. Pressure at this point pushes the high knock- down p1ug downward against the top of the main-pressure regulator valve. There is no effect on main pressure when lockup is en- gaged because lockup apply pressure (main) is already exerting an equal downward force on the main-pressure regulator valve. How- ever, if the lockup clutch should disengage, the high knockdown plug would continue to push downward on the main-pressure regulator valve. Thus, main pressure is the same in fourth gear whether operation is lockup or converter. This is the only gear in which this is true. In all other gears, lockup operation causes a lowering of main pressure. 35. HYDRAULIC SYSTEM FUNCTION – REVERSE 1 GEAR (fig. 11) Note. Refer to par. 51 and fig. 27 for the torque path through the power train. a. Hydraulic system conditions in re- verse 1 gear are the same as described for neutral in par. 30, above, and illustrated in fig. 6, except that the reverse-range clutch is engaged and the vehicle is moving in reverse. b. When the manual selector valve is in reverse 1 position, the reverse-range clutch is engaged and a branch of the clutch apply line directs main pressure to the lower end of the regulator plug. This pressure pushes up- ward on the regulator plug which, in turn, pushes upward on the main-pressure regulator valve. Thus, the plug’s upward force assists the regulator valve springs and increases main pressure. c. At higher speeds, the shift inhibitor plunger wi11 extend and block any shift to neutral or a forward gear. d. In reverse gear, the brake coolant pump rotates in a reverse direction. Thus, no brake coolant can be pumped. 36. HYDRAULIC SYSTEM FUNCTION – REVERSE 2 GEAR (fig. 12) Note. Refer to par. 52 and fig. 28 for the torque path through the power train. a. Hydraulic system conditions in re- verse 2 gear are the same as those for reverse 1 gear except that the power train output drive is through the output clutches rather than through the geared steer clutches. b. In reverse 2 gear, no signal pressure exists under the drive clutch relay valve. Spring pressure holds the valve downward, in which position steer pressure is directed to the right- and left-output clutches. Reverse 2, third and fourth signal pressure is directed to the lower side of the steer relay valve. This pushes the valve upward against spring pres- sure and alines the steer circuit for geared steer. 37. HYDRAULIC SYSTEM FUNCTION - LOW RANGE, STEER a. First Gear, Full-right Steer (fig. 13) Note. Refer to par. 53 and fig. 29 for the torque path through the power train. (1) The hydraulic system will function in first-gear steer in the same manner as de- scribed for first-gear straight travel in par. 31, above, except for the position of the steer valves and the flow of oil to the drive clutches and brakes. (2) In right steer, the steer control shaft is rotated clockwise. This rotation moves the right- steer valve downward while the left-steer valve moves upward. The downward move- ment of the right-steer valve blocks the flow of steer pressure (in the upper passage), pre- venting its being directed to the right-drive clutch feed line. In the lower steer pressure passage, a port is uncovered which allows steer pressure to enter the steer regulator valve bore and to flow to the right-steer feed line. The pressure in the right-steer feed line is regulated by the action of the lower part of the steer valve assembly. When steer pres- sure enters the right-steer valve bore, it exerts an upward pressure on the steer regu- lator valve. Upward movement of the steer regulator valve throttles the in-flow of steer pressure. Thus, the degree of downward movement of a steer valve determines steer 35