TM-9-2520-254-34 Direct Support for M113 TX100-1 Transmission 2520-00-066-4240 Download

c. Front Governor (Gl) Circuit (blue, black— fig. 2-3). (1) Pressure or flow in the front governor circuit is caused by the front fluid velocity governor (para 2-7). The three branches of the circuit connect with the main regulator plug, lockup valve plug, and a ball check valve at the right of the manual selector valve. (2) In neutral (and reverse) the ball check valve is always open (downward) because there is no pressure below the ball to seat it (upward). The line, below the ball, exhausts around the manual selector valve stem. Thus, there is a flow, but no pressure in the front governor circuit. As a result, the main regulator plug and lockup valve plug remain down. Main pressure is not modulated by front governor pressure, and lockup cannot occur in neutral operation. 2-15. Hydraulic System—Low-Range Oper- ation a. Main Pressure Circuit (red—fig. 2-4). (1) Figure 2-4 illustrates low-range operation of the transmission while engine throttle is open and the lockup clutch is engaged. The explanations of circuits and components, below, will refer to previous explanations where applicable. (2) Oil is pumped into the main pressure circuit by both oil pumps (when vehicle is moving forward) in low-range operation. The rear pump check valve is open (upward) when the rear pump is rotating. Oil is distributed as described in paragraph 2-14a (2). (3) At the throttle valve, during full-throttle operation as illustrated, the throttle valve (TV) and throttle (T) circuits are charged. Refer to f and g below for explanations of these circuits. (4) At the manual selector valve, main pressure is directed to four points. These are the front governor check valve ball, low-intermediate shift valve. high-intermediate inhibitor circuit, and intermediate-low inhibitor circuit. Main pressure seats the check valve ball (upward) in the front governor (G1) passage and prevents governor pressure from exhausting. (5) At the low-intermediate shift valve, main pressure divides to two branches. The upper branch is blocked but the pressure exerted against valve lands of different diameters exerts a downward force on low-intermediate shift valve. This pressure acts only when the valve is downward and prevents cycling of the valve. A similar downward force, resulting from unequal valve land diameters, is exerted in the lower branch. These forces act only when the valve is downward. The lower branch connects. when the low-intermediate shift valve is downward, with the low-range clutch (e below). (6) Oil flowing to the high-intermediate inhibitor circuit is restricted by an orifice before it reaches the inhibitor valve and the intermediate- high blocker plug. Refer to paragraph 2-20a for an explanation of the high-intermediate inhibitor circuit. (7) Oil flowing to the intermediate-low inhibitor circuit is restricted by an orifice before it reaches the inhibitor valve and low-intermediate blocker plug. Refer to paragraph 2-21a for an explanation of the intermediate-low inhibitor circuit. (8) At the lockup valve, which is in lockup position (upward), main pressure divides to two branches. The lower branch is still blocked as in converter operation. The upper branch is open to lockup feed. Lockup feed also divides to two branches. The upper branch directs pressure, through an orifice, to the area between the main regulator valve and regulator plug. Here, main pressure forces the plug downward, and forces the main regulator valve upward. This decreases main pressure. (9) The lower branch of lockup feed enters the flow valve bore and supplies pressure for lockup operation (except when flow valve is downward). Refer to i below for explanation of the lockup circuit. (10) Main pressure enters the flow valve bore and acts as described in paragraph 2-14a (6). (11) At the main regulator valve, main pressure raises the valve as described in paragraph 2-14a (7). However, the valve is moved farther upward in the bore than shown in figure 2-3, allowing oil to escape to the sump as well as to the converter-in circuit. Refer to b below for ex- planation of the converter-in circuit during lockup operation. (12) At the trimmer valve, main pressure enters the valve bore at two points. At the upper point (orifice at right side of bore), oil fills the area above the trimmer plug. Main pressure is at full value in this area because no oil can escape past the extender valve ball held downward by main pressure. (13) At the lower end of the trimmer valve, main pressure enters the trimmer valve bore, connects with the area within the valve through an orifice. and exerts equal pressure above and below the valve. The springs above and below the trimmer plug hold the trimmer plug and valve in the positions illustrated. The trimmer is set for action when in this condition. Refer to paragraph 2-16i for explanation of trimmer operation. 2-11