FIRST SPEED FORWARD - TM-5-3805-263-14P-2

FIRST SPEED FORWARD - TM-5-3805-263-14P-2_287

FIFTH SPEED REVERSE - TM-5-3805-263-14P-2_289

TM-5-3805-263-14P-2 Grader Heavy Road Motorized Type I Nonsectionalized Type II Sectionalized Manual
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TRANSMISSION HYDRAULIC CONTROLS SYSTEMS OPERATION TM 5-3805-263-14&P-2 FIRST SPEED FORWARD When the selector lever is moved from NEU- TRAL to FIRST FORWARD, the pilot selector valve (16) lets the signal pressure in passages (A) and (F) go to the reservoir and sends signal pressure to passages (B) and (G). When the signal pressure in passage (F) goes to the reservoir, the spring force on the speed selector spool (36) moves the spool to the left and lets the pressure oil in the passage for the No. 3 clutch (38) go to the reservoir. The signal pressure in passage (B) moves the speed selector spool (35) to the right and lets the pressure oil in the passage for the No. 7 clutch (37) go to the reservoir. The No. 3 and No. 7 clutches are now not engaged. When the speed selector spools (18) and (35) are m o v e d t o t h e p o s i t i o n s s h o w n b y t h e s i g n a l pressure in passages (G) and (B), the passages to clutch No. 5 (23) and No. 6 (30) are open to system pressure. With the speed selector spool (35) in the position shown, the passage (27) from the left end of the differential, check, and safety spool (15) (open to the reservoir in NEUTRAL) has pressure oil. This pressure oil moves the differential, check, and safety valve (15) to the right and lets pressure oil go to the direction clutches. Since the direction selector valve (28) is in the position shown, pressure oil will go to the passage (33) for the No. 1 clutch. When the shift is made from NEUTRAL to FIRST FORWARD and the No. 5 and No. 6 clutches are being filled, the spring pressure moves the modulating reducing valve (31) to the right. As the clutches fill, the system pressure has an increase. The increase in pressure works against the slug in the modulating reducing valve (31) and the valve moves to the left to stop the increase in pressure. With this higher pressure, the load piston (32) moves to the right and the spring force between the modulating reducing valve and the load piston has an increase. The increase in spring force moves the modulating reducing valve (31) to the right and this lets the system pressure have an increase. This cycle takes place again and again until the system pressure is at a maximum. This gradual increase in pressure is modulation. The modulating reducing valve (31) gives modulation for all the clutches (speed and direction). The differential, check and safety valve (15) causes a pressure difference of 60 psi (415 kPa) between the P1 pressure and the P2 pressure. The P2 pressure to the direction clutches is always 60 psi (415 kPa) less than the P1 pressure to the speed clutches. This pressure difference lets the speed clutches engage first. The direction clutches engage last and take the load. When P1 pressure is at a maximum of approximately 340 psi (2350 kPa) (controlled by the main relief valve), the P2 pres- sure is at approximately 280 psi (1950 kPa) with the engine at HIGH IDLE. When the engine is at LOW IDLE, P1 pressure is approximately 310 psi (2120 kPa) and P2 pressure is approximately 250 psi (1720 kPa). The shift is now complete. 2-22

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