MOTOR G. 4H9255 - Caterpillar

General Information
Illustration 1 g00649144
The hoist control valve is located at the right rear of the tractor. Open the transmission guard in order to access the hoist control valve.
Illustration 2 g00649143
Hoist control valve (1) Eye (2) Control spool (3) Hole (4) Work port (rod end of the hoist cylinders) (5) Passage (6) Hole (7) Passage (8) Tank port (9) Passage (10) Hole (11) Hole (12) Passage (13) Work port (Head end of the hoist cylinders) (14) Hole (15) Check valve (16) Spring (17) Detent groove (18) Spring (19) Pilot port (20) Large adjusting screw (21) Detent balls (22) Plunger face (23) Plunger (24) Tank passage (25) Spring (26) Pilot valve (27) Restrictor (28) Chamber (29) Inlet port (30) Inlet port (31) Holes (32) Spool (33) Spool face (34) Relief valve cartridge (35) Tank passageThe linkage for the hoist control lever is attached to control spool (2) at eye (1). When the hoist control lever is placed in the RAISE position, control spool (2) is moved to the left. When the hoist control lever is placed in the LOWER position, control spool (2) is moved to the right. Spring (18) is compressed in both positions and spring (18) will return control spool (2) to the HOLD position when the hoist control lever is released.Oil from the steering control valve enters the hoist control valve through inlet port (29) and oil from the vane pump enters the hoist control valve through port (30). The inlet oil flows to control spool (2) through restrictor (27) and chamber (28). Chamber 28 is inside of relief valve cartridge (34) .FLOAT Position
When the hoist control lever is placed in the FLOAT position, control spool (2) is moved to the right until detent balls (21) engage in detent groove (17). Work ports (4, 13) are connected to tank port (8) through passages (5, 12) and holes (6, 9, 11) in control spool (2) .The hoist control valve will remain in the FLOAT position until the hoist control lever is pulled up in order to disengage the detent. This will allow spring (18) to return control spool (2) to the HOLD position.RAISE Position
When the hoist control lever is placed in the RAISE position, control spool (2) is moved to the left. Oil from the inlet ports flows through holes (11). This offsets check valve (15) to the right and the oil flows through holes (14) and passage (12) to work port (13). As the hoist cylinders extend in order to raise the dump body, oil from the rod ends of the hoist cylinders flows into the hoist control valve through work port (4), passage (5), and holes (6, 3) to tank passage (35). If the oil supply fails for any reason, spring (16) will move check valve (15) to the left in order to prevent a reverse flow of oil from the head ends of the hoist cylinders through holes (14). The dump body will be held in the raised position.HOLD Position
When the hoist control lever is placed in