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

CHAP 2, SEC II DESCRIPTION AND OPERATION OF PAR 19-20 MAIN TRANSMISSION ASSEMBLY engaged as drive clutches. When the range selector valve (refer to par. 21, below) is in first gear, neutral or reverse 1 gear position, a signal pressure is directed to the end of the valve opposite spring 75. This moves the valve against spring 75 and pin 74. In this position, the hydraulic circuit engages the right- and left-geared steer clutches and exhausts the right- and left-output clutches. (2). When the selector valve is in second, third, fourth or reverse 2 gear po- sition, the signal pressure is exhausted and spring 75 moves the valve to the opposite end of its bore. In this position, the hy- draulic circuit engages the output clutches and exhausts the geared steer clutches. (3) Valves 64 and 65 are the steer relay valves. Their position in the valve body bore determines whether clutch brake steer or geared steer is effective. When the range selector valve is in first or second gear, neutral or reverse 1 posi- tion, no signal pressure is present at the end of the valve bore opposite the spring end. As a result, spring 66 moves both valves to the end of the bore opposite the spring. In this position, the hydraulic cir- cuit connects the steer valves (refer to par. 20, below) to the brakes and the ef- fective drive clutches. Thus, the hydraulic circuit is arranged for clutch-brake steer. (4) When the range selector valve is in third, fourth or reverse 2 gear posi- tion, a signal pressure at the end of the bore opposite the spring pushes the valves against spring 66. In this position, the hy- draulic circuit connects the steer valves to the output clutches and geared steer clutches. Thus, the hydraulic circuit is ar- ranged for geared steer. Movement of the steer valves, while operating with clutch- brake steer, will release a driving clutch (right or left, depending upon direction of steer applied) and apply the brake at the same side. This causes a turn toward the side at which the brake is applied. (5) Movement of the steer valves, while operating with geared steer, will release an output clutch (right or left, depending upon direction of steer applied) and engage a geared steer clutch on the same side. This slows the affected side 20 Change 2 and causes the vehicle to steer toward that side. 20. STEER VALVE BODY ASSEMBLY a. Components (fig. 382, fold-out 11) (1) The steer valve body assembly includes body 40, steer valve assemblies 24 through 30 and 33 through 39, plugs 31 and 32, valve assembly 14, springs 12 and 13, cover 10, shaft assembly 45 and indicator 21. Steer valve assemblies 24 through 30 and 33 through 39 operate in bores of valve body 40. Steer pressure regulator valve assembly 14 operates in a bore of the valve body. Plugs 31 and 32 close the steer valve bores. Cover 10 closes the opposite ends of the steer valve bores and compresses springs 12 and 13 against reg- ulator valve assembly 14. (2) Shaft assembly 45 has two lugged fingers which engage grooves at the ends of steer valves 29 and 34. A splined shaft extends through the top of the valve body and a steer indicator is installed on the splines. A detent ball 43 and spring 42 stabilizes the valves in “no steer” position. b. Operation (fig. 372, fold-out 1 and fig. 382, fold-out 11) (1) Steer pressure regulator valve assembly 14, moving lengthwise against springs 12 and 13, produces a constant pressure (reduced from main) to apply steer clutches or brakes (depending upon method of steer being used). Steer valves 29 and 34 are moved simultaneously lengthwise in opposite directions to direct steer pressure to the proper clutch or brake. This movement results from rota- tion of steer shaft assembly 45. (2) The direction of movement of the valves determines the direction of steer. The degree of movement of the steer valves determines the degree of steer application. Each steer valve assem- bly constitutes a pressure regulator. Thus, a slight movement of a steer valve assembly will direct a greatly reduced pressure to the steer clutch or brake being applied. Greater movement will increase the pressure. Full movement