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

PAR 20-21 DESCRIPTION AND OPERATION OF CHAP 2, SEC II MAIN TRANSMISSION ASSEMBLY will result in maximum pressure. Steer valves 29 and 34, and passages in valve body 40, are so constructed that either valve, moving toward cover 10, directs pressure to the clutch or brake being ap- plied while exhausting the clutch which must be released at the same side of the transmission. Movement of either valve 29 or 34 toward the opposite end of its bore has no effect on the brake or clutch which it supplies or exhausts. Movement of either steer regulator valve 26 or 37 away from cover 10 will direct coolant to the steering member (brake or clutch) being applied for steer. 21. CONTROL VALVE BODY ASSEMBLY a. Components (fig. 383, fold-out 12) (1) The control valve body assem- bly includes valves and other components which perform four different functions. All of these components are installed in a common valve body 54. The range selector valve group includes valve assembly 75, selector shaft assembly 56, indicator 49, ball 59 and spring 60. Valve assembly 75 operates in a bore of the valve body. Its lengthwise movements are manually con- trolled by shaft assembly 56 which engages a slot in the stem of the valve. Ball 59 and spring 60 retain the lever in any posi- tion to which it is manually shifted. (2) Lockup cutoff valve 80 is a simple, spool-type valve which moves lengthwise in its bore. Its movement is controlled entirely by hydraulic pressures to which it is subjected. (3) The downshift inhibitor group includes inhibitor plunger 79, spring 78 and valve 76. Plunger 79 is fitted in a bore of the valve body which is alined with a stepped projection on shaft assembly 56. Spring 78 is installed on plunger 79 and acts against retaining ring 77 on the plun- ger. The plunger seats against valve 76. (4) The throttle valve 61 and throttle regulator valve assembly 63 fit into a common bore and are separated by spring 62. Both valves act against spring 68. Both valves are moved lengthwise toward spring 68 by shaft assembly 58. b. Operation (fig. 372, fold-out 1 and fig. 383, fold-out 12) (1) For range selection, the ve- hicle operator shifts the range selector control to the desired range. Selector shaft assembly 56, being linked to the operator’s control, moves to a correspond- ing position. In each range position, hy- draulic pressure is directed to the range clutch to be applied. Simultaneously, other range clutches are exhausted through passages controlled by valve 75. (2) When any shift from one range to another occurs, the oil required to apply the oncoming clutch must pass through the bore in which lockup clutch cutoff valve 80 operates. This flow moves the valve to a position which interrupts the flow of oil to the lockup clutch and exhausts the lockup clutch pressure. When the oncoming range clutch fills, the rising pressure returns valve 80 to its original position and restores pressure to the lock- up clutch. (3) Governor pressure acts against shift inhibitor valve 76. When the speed of the turbine shaft is sufficient, governor pressure will overcome the resistance of spring 78. Valve 76 then pushes plunger 79 into the path of the stepped lug on shaft 56, preventing its movement to a lower range position. (4) Throttle valve 61 and throttle regulator valve assembly 63 are acted upon by three forces. Throttle valve shaft assembly 58 pushes throttle valve 61 into its bore. Throttle regulator valve assembly 63 is, in turn, pushed by spring 62 against spring 68. Hydraulic pressure reacts against the throttle regulator valve. Two control pressures (T and TV) arise in the action of these two valves. TV pressure results from the position of throttle regu- lator valve assembly 63 and compression of spring 62. T pressure results from the position of throttle valve 61. TV pressure varies according to throttle opening, be- ginning early in throttle movement and continuing through full throttle. T pres- sure is merely TV pressure introduced to the hydraulic system during the late phases of throttle opening. 21