General Information

SMCS Code: 4300

Schematic for the Steering Hydraulic System (STIC Steer Machines)
(1) Steering cylinders. (2) Secondary steering pump (if equipped). (3) Secondary steering diverter valve (if equipped). (4) Crossline relief valves. (5) Steering control valve. (6) Check valves. (7) Oil cooler. (8) Left neutralizer valve. (9) Right neutralizer valve. (10) Pilot control valve. (11) Pilot oil pressure reducing valve. (12) Dual pilot check valve. (13) Brake and pilot pump. (14) Steering pump. (15) Vacuum breaker/relief valve. (16) Selector and pressure control valve. (17) Steering secondary lockout valve (door neutralizer). (18) Hydraulic tank group. (19) Hydraulic oil filter group. (20) Manifolds. (AA) Pressure test point for steering system.

Location of the Steering Hydraulic System Components
(1) Steering cylinders. (5) Steering control valve. (7) Oil cooler. (8), (9) Neutralizer valves. (10) Pilot control valve. (11) Pilot oil pressure reducing valve. (12) Dual pilot check valve. (13) Brake and pilot pump. (14) Steering pump. (16) Selector and pressure control valve. (17) Steering secondary lockout valve (door neutralizer). (18) Hydraulic tank group.

The steering hydraulic system is made up of two basic circuits; the pilot circuit and the high pressure circuit. When the machine is equipped with the optional wheel steer attachment, secondary steering attachment or reversible steering attachment, the steering system also includes these additional circuits.

The main components of the pilot circuit are hydraulic tank (18), brake and pilot pump (13), pilot oil pressure reducing valve (11), steering secondary lockout valve (door neutralizer) (17), pilot control valve (10), dual pilot check valve (12), neutralizer valves (8) and (9), steering control valve (5), selector and pressure control valve (16), hydraulic oil filter group (19) and various lines.

The main components of the high pressure circuit are hydraulic tank (18), steering pump (14), steering control valve (5), crossline relief valves (4), steering cylinders (1), oil cooler (7), hydraulic oil filter group (19) and various lines.

The main components of the secondary steering circuit (if equipped) are hydraulic tank (18), secondary steering pump (2), secondary steering diverter valve (3) and various lines.

Location of the Hydraulic Tank and Filter Group
(18) Hydraulic tank. (19) Hydraulic oil filter group (behind cover). (21) Filler cap.

Hydraulic tank (18) is located in the middle of the right side of the machine. Hydraulic oil filter group (19) is mounted inside hydraulic tank (18). Oil is placed into the tank through filler cap (21).

Location of the Steering, Brake and Pilot Pump
(13) Brake and pilot pump section. (14) Steering pump section.

Brake and pilot pump (13) and steering pump (14) are mounted on the torque converter updrive housing.

Location of the Pilot Oil Pressure Reducing Valve
(11) Pilot Oil Pressure Reducing Valve.

Pilot oil pressure reducing valve (11) is mounted on the left side of the rear frame in the transmission compartment.

Location of the Steering Secondary Lockout Valve (STIC Steer Machines)
(17) Steering secondary lockout valve (door neutralizer).

Steering secondary lockout valve (17) is mounted on the operator's station door.

Location of the Pilot Control Valve
(10) Pilot control valve.

Pilot control valve (10) is mounted on the operator's station door.

Location of the Neutralizer Valves
(8) Left neutralizer valve. (9) Right neutralizer valve.

Left neutralizer valve (8) and right neutralizer valve (9) are located on the rear frame near the upper articulation hitch.

Location of the Steering Control Valve
(5) Steering control valve.

Steering control valve (5) is located on the rear frame, rearward of the articulation hitch.

Location of the Steering Cylinder
(1) Steering cylinder.

Steering cylinders (1) are located on either side of the lower articulation hitch.

Location of the Crossline Relief Valve
(4) Crossline relief valve.

Crossline relief valves (4) are mounted on the steering cylinders.

Location of the Oil Cooler
(7) Oil cooler.

Oil cooler (7) is mounted on the outside of the radiator. Access is gained by opening the guard on the rear of the machine.

Location of the Secondary Steering Pump
(2) Secondary steering pump (if equipped).

Secondary steering pump (2) is mounted on the transfer gearbox on the front of the transmission.

Location of the Secondary Steering Diverter Valve
(3) Secondary steering diverter valve (if equipped).

Secondary steering diverter valve (3) is mounted on the right side of the transmission.

Steering System (Pilot Oil)

SMCS Code: 4300-PS

Schematic for the Steering Pilot System (STIC Steer Machines)
(1) Steering control valve. (2) Pilot oil return. (3) Pilot oil line. (4) Pilot oil line. (5) Left neutralizer valve. (6) Right neutralizer valve. (7) Pilot control valve. (8) Dual pilot check valve. (9) Pilot oil pressure reducing valve. (10) Check valve. (11) Check valve. (12) Brake and pilot pump. (13) Vacuum braker/relief valve. (14) Selector and pressure control valve. (15) Steering secondary lockout valve (door neutralizer). (16) Hydraulic tank. (17) Hydraulic oil filter group. (18) Check valve. (AA) Pressure test point for steering system.

The pilot circuit controls the movement of the steering control valve spool in steering control valve (1).

With the engine running, oil flows from hydraulic tank (16) to pilot oil pump (12). The pump is a gear-type pump.

Pressure oil then flows through check valve (10) to pilot oil pressure reducing valve (9). Part of the oil also flows from the pump and check valve to the braking system.

From pilot oil pressure reducing valve (9), oil flows through check valve (18) to selector and pressure control valve (14).

As long as the pilot pump is supplying oil to the pilot system, selector and pressure control valve (14) will block the flow of alternate oil into the steering pilot system.

If the pilot pump fails, or oil is not available, then selector and pressure control valve (14) will allow alternate pilot oil to flow into the steering pilot system from the lift cylinders. If oil is not available from the lift cylinders, selector and pressure control valve (14) will allow alternate pilot oil to flow into the steering pilot system from steering control valve (1).

From the selector and pressure control valve, part of the oil flows on to the implement pilot system. The rest of the pilot oil flows through steering secondary lockout valve (15) to pilot control valve (7). The steering secondary lockout valve (door neutralizer) prevents pilot oil from flowing to pilot control valve (7) when the operator's station door is open.

When the STIC control lever is moved to either turn direction, pilot control valve (7) routes oil to dual check valve (8). Then the oil flows to either left neutralizer valve (5) or right neutralizer valve (6), depending on which direction the machine is turning.

From the neutralizer valves, oil flows through line (3) or (4) to control valve (1). The pilot oil acts on one side or the other of the control valve spool causing the spool to move. When the spool moves, it allows high pressure oil from the steering pump to flow to the steering cylinders.

Return oil from the control valve flows through line (2) to hydraulic tank (16). Return oil from pilot control valve (7) and neutralizer valves (5) and (6) also flows back to the hydraulic tank.

Gear Pump (Pilot and Braking)

SMCS Code: 5073-P&B

Location of the Steering, Brake and Pilot Pump
(1) Brake and pilot pump section. (2) Steering pump section.

Brake and pilot pump (1) is part of a two-section, gear-type pump mounted on the torque converter updrive housing. The brake and pilot pump is a fixed displacement pump which supplies oil to the parking brake circuit, service brake circuit, implement pilot circuit and STIC steering pilot circuit.

Pressure Reducing Valve (Pilot Hydraulic System)

SMCS Code: 5467-PS

Location of the Pressure Reducing Valve
(1) Pilot oil pressure reducing valve.

The pilot oil pressure is controlled by pilot oil pressure reducing valve (1). The pilot oil system will constantly operate at the pressure reducing valve pressure setting.

Pilot Oil Pressure Reducing Valve
(1) Valve. (2) Drain outlet. (3) Inlet. (4) Reduced pressure outlet.

Pilot oil from the brake and pilot pump enters the pilot oil pressure reducing valve through inlet (3). Pilot oil pressure reducing valve (1) is a cartridge type valve that maintains pilot pressure to the implement and steering circuits at 3515 ± 70 kPa (510 ± 10 psi).

Reduced pressure oil flows to the selector and pressure control valve through outlet (4). Excess oil returns to the hydraulic tank through outlet (2).

Steering Secondary Lockout Valve

SMCS Code: 4330

Steering Secondary Lockout Valve
(1) Outlet port. (2) Inlet port. (3) Stem. (4) Striker plate. (5) Return port.

The steering secondary lockout valve stops the flow of pilot oil to the pilot control valve when the operator's station door is open. This stops the steering action while an operator is mounting or dismounting the machine.

The lockout valve is mounted on the operator's station door. Striker plate (4) is mounted on the inside of the operator's station.

When the operator's station door is fully closed, pilot oil flows to the pilot control valve through the steering secondary lockout valve. As the operator's station door moves to the fully closed position, the cam roller on stem (3) pushes against striker plate (4). Stem (3) overcomes spring tension and moves in, allowing the flow of pilot oil through inlet port (2) around stem (3) to outlet port (1) and on to the pilot control valve. Movement of the steering control will cause the machine to steer in the selected direction.

When the operator's station door is opened, pilot oil flow to the pilot control valve is stopped by the steering secondary lockout valve. As the operator's station door moves to the open position, the cam roller on stem (3) moves away from striker plate (4). Spring tension moves stem (3) out, stopping the flow of pilot oil from inlet port (2) to outlet port (1). This stops the flow of oil to the pilot control valve. The stem allows oil flow from outlet port (1) through return port (5) to tank. The machine will not steer in either direction if there is any movement of the steering control.

Steering Pilot Control Valve (STIC Steer)

SMCS Code: 4342

Steering Pilot Control Valve
(1) Handle. (2) Link. (3) Link. (4) Plunger. (5) Plunger. (6) Spring. (7) Spring. (8) Cap. (9) Cap. (10) Spring seat. (11) Spring seat. (12) Spring. (13) Spring. (14) Port to tank. (15) Spring. (16) Spring. (17) Passage. (18) Passage. (19) Spool. (20) Spool. (21) Port to neutralizer valve for left turn. (22) Inlet from steering secondary lockout valve (door neutralizer). (23) Port to neutralizer valve for right turn.

With the engine running and the operator's station door closed, pilot oil flows from the steering secondary lockout valve (door neutralizer) to the pilot control valve. Oil enters the valve at inlet port (22).

When the steering control is in the STRAIGHT AHEAD position, centering springs (6), (7), (12), (13), (15) and (16) keep the pivot plate in the CENTERED position. Pilot oil flows through inlet (22) to metering spools (19) and (20). In this position, the spools block the flow of oil to the steering control valve. This causes the oil to flow back to the hydraulic oil tank.

When the steering control is moved to the LEFT TURN position, the pivot plate causes link (2) to move plunger (4) downward. As the plunger moves downward, the plunger overcomes the force of spring (6). This causes the spring to move downward. As the plunger moves downward through cap (8), the plunger also causes spring seat (10), spring (12), spring (15), and spool (19) to move downward.

At the same time, the pivot plate causes link (3) to move plunger (5) upward. As the plunger moves upward, spring (7) moves upward. As the plunger moves upward through cap (9), spring (13) and spring seat (11) move upward. Spring (16) moves spool (20) upward.

When spool (19) moves downward, passage (17) opens. Oil can now flow from inlet port (22) into passage (17). The oil then flows through passage (17) past spool (19). The oil then moves out of port (21).

The oil flows from port (21) to the neutralizer valve for left turns. Next, the oil flows to the steering control valve.

Oil that flows from the steering control valve flows through the neutralizer valve for right turns. The oil then flows from the neutralizer valve for right turns to port (23).

Because spool (20) is up, the oil can flow past the spool into the return oil passage. The oil flows through the passage and out port (14) back to the hydraulic oil tank.

When the steering control is moved to the RIGHT TURN position, the pivot plate causes link (3) to move plunger (5) downward. As the plunger moves downward, spring (7) moves downward. As the plunger moves downward through cap (9), the plunger causes spring seat (11), spring (13), spring (16), and spool (20) to move downward.

At the same time, the pivot plate causes link (2) to move plunger (4) upward. As the plunger moves up, spring (6) moves up. As the plunger moves up through cap (8), the plunger also causes spring (12) and spring seat (10) to move upward. Spring (15) moves spool (19) upward.

When spool (20) moves down, passage (18) opens. Oil can now flow from inlet port (22) into passage (18). The oil then flows through passage (18), past spool (20), and out port (23).

The oil flows from port (23) to the neutralizer valve for right turns. The oil then flows to the steering control valve.

Oil from the steering control valve flows through the neutralizer valve for left turns. The oil then flows from the neutralizer valve into port (21).

Because spool (19) is up, the oil can flow past the spool into the return oil passage. The oil then flows out of port (14) to the hydraulic oil tank.

Check Valve (Steering Dual Pilot)

SMCS Code: 5067-ZH

Schematic for the Dual Pilot Check Valve, the Steering Control Valve and the Neutralizer valves
(1) Purge orifice. (2) Spring. (3) Valve spool. (4) Steering control valve. (5) Left neutralizer valve. (6) Right neutralizer valve. (7) Dual pilot check valve. (8) Check valve. (9) Check valve.

Dual pilot check valve (7) allows valve spool (3) to shift if a purge orifice becomes plugged. Oil flows from the steering pilot control valve, through respective check valve (8) or (9), through left neutralizer valve (5) or right neutralizer valve (6) and into the pilot chamber on steering control valve (4). This moves spool (3) against return spring (2). If the flow from the pilot control valve is shut off, the check valve closes. This prevents flow back to the pilot control valve. This also traps oil in the pilot chamber of steering control valve (4). As return spring (2) pushes spool (3) to the HOLD position, the oil that is trapped in the pilot chamber is forced back to the tank through purge orifice (1). This allows spool (3) to smoothly return to the HOLD position.

If purge orifice (1) is plugged, oil will be trapped in the pilot chamber of steering control valve (4) and spool (3) will remain shifted. In order to overcome this problem, pilot oil opens the other check valve when the pressure in the pilot chamber is increased. The pressure in the pilot chamber also increases when you move the STIC control lever fully to either direction. Oil then flows from the pilot chamber, through the neutralizer valve and dual pilot check valve to the hydraulic tank.

Steering Neutralizer Valve (STIC Steer)

SMCS Code: 4330

Neutralizer Valve in the OPEN Position
(1) Striker. (2) Inlet. (3) Outlet. (4) Stem. (5) Spring.

The neutralizer valve stops the flow of pilot oil to the steering control valve at the end of a complete turn. This stops the steering action before the machine turns against the frame stops.

Striker (1) for each valve is mounted on the front frame. Both of the neutralizer valves are mounted on the rear frame. The right and left neutralizer valves and strikers are identical.

Schematic for the Neutralizer Valves
(1) Striker. (2) Inlet. (3) Outlet. (4) Stem. (5) Spring. (6) Left neutralizer valve. (7) Oil line. (8) Oil line. (9) Right neutralizer valve. (10) Pilot oil line. (11) Pilot oil line.

Pilot oil flows from the pilot control valve to either the right or left neutralizer valve before flowing to the steering control valve. Oil flows from the pilot control valve through line (10) or (11) into neutralizer valve (6) or (9) through inlet port (2). Then the oil flows around stem (4) and through outlet port (3) into line (7) or (8). Then the oil flows to the steering control valve.

When the steering control is moved to the right turn position, and the machine is turned as far right as it can turn, striker (1) comes in contact with stem (4) of the right neutralizer valve. The striker forces the stem to compress spring (5) and moves the stem until pilot oil can not flow from port (2) to port (3). This stops the flow of pilot oil through line (8) and relieves the pilot oil pressure at the end of the steering control valve spool to tank.

When the flow of pilot oil stops acting on the spool in the steering control valve, the control valve spool returns to the HOLD position. This causes the steering action of the machine to stop.

When the steering control is moved back to the left, return oil from the end of the steering control valve spool flows through line (8) into port (3) of the right neutralizer valve. Stem (4) allows oil flow from port (3) to tank. This allows the steering control valve spool to move and the machine begins to turn to the left.

As the machine moves to the left a small amount, striker (1) will move away from stem (4). Spring (5) tension acts against stem (4) and moves it back into the open position.

The left neutralizer valve operates in exactly the same manner as the right neutralizer valve.

Steering System (High Pressure Oil Circuit)

SMCS Code: 4300-HQ

Schematic for the Steering Hydraulic System (STIC Steer Machines)
(1) Left steering cylinder. (2) Right steering cylinder. (3) Secondary steering pump (if equipped). (4) Secondary steering diverter valve (if equipped). (5) Crossline relief valve. (6) Crossline relief valve. (7) Steering control valve. (8) Check valve. (9) Oil cooler. (10) Orifice. (11) Pilot control valve. (12) Steering pump. (13) Vacuum breaker/relief valve. (14) Selector and pressure control valve. (15) Hydraulic tank. (16) Hydraulic oil filter group. (AA) Pressure test point for steering system.

With the engine running, oil flows from hydraulic tank (15) to pump (12). The two section gear type pump has one pump section for the steering circuit and a smaller pump section for the pilot circuit and brakes. The oil flows in two paths, one path to the steering circuit and one to the pilot and brake circuit.

The steering pump sends oil to steering control valve (7). On machines equipped with secondary steering, oil flows through the check valve in secondary steering diverter valve (4) into steering control valve (7).

In the secondary steering diverter valve, check valves control the flow of the oil. When the steering pump supplying oil to the diverter valve is working properly, the check valves allow oil to flow into and through the secondary steering diverter valve.

When the steering pump supplying oil to the secondary steering diverter valve is not working properly and the machine is moving in either the forward or reverse direction, the check valves in the diverter valve allow oil from secondary steering pump (3) to flow through secondary steering diverter valve (4), into steering control valve (7).

Part of the oil flows out of steering control valve (7), through check valve (8) to selector and pressure control valve (14). This oil can be used as an alternative source of pilot oil if the pilot oil pump and the lift cylinders can not supply sufficient pilot oil.

When the machine is in the straight ahead travel position, the rest of the oil in the control valve cannot flow past the control valve spool. Then the oil flows out of the control valve to oil cooler (9) back to hydraulic tank (15). When the oil is cold, or the oil cooler is blocked, orifice (10) allows the oil to flow from the control valve back to the hydraulic tank.

Under normal operating oil temperature, the oil flows through oil cooler (9) and back to hydraulic tank (15).

When the machine is turning, oil from steering control valve (7) flows to steering cylinders (1) and (2). If an external force (for example, a tire strikes a large rock or hole) acts on the steering cylinders, crossline relief valves (5) and (6) prevent excessive pressure in the steering cylinders and lines. When the steering cylinder pressure increases to the crossline relief valve setting, the valve will open and allow oil in one end of the steering cylinder to flow into the other end of the cylinder.

Steering Pump

SMCS Code: 5073-ZH

Location of the Steering, Brake and Pilot Pump
(1) Brake and pilot pump section. (2) Steering pump section.

Steering pump (2) is part of a two-section, gear-type pump mounted on the torque converter updrive housing. The steering pump is a fixed displacement pump which supplies oil to the steering control valve.

Steering Control Valve (STIC Steer)

SMCS Code: 4307

HOLD Position

Steering Control Valve in the HOLD Position
(1) Alternate pilot oil port. (2) Inlet. (3) Shuttle valve. (4) Port to tank. (5) Flow control valve. (6) Passage. (7) Relief valve. (8) Passage. (9) Return passage. (10) Chamber. (11) Orifice. (12) Passage from left neutralizer. (13) Spool. (14) Passage from right neutralizer. (15) Orifice. (16) Passage. (17) orifice. (18) Port for left turn. (19) Port for right turn. (20) Drain. (21) Spring.

The flow of pilot oil to either end of spool (13) stops when either the STIC control lever movement stops, or one of the neutralizer valves is activated. When no pilot oil is acting on an end of the spool, centering spring (21) returns the spool to the HOLD position. As the spool returns to hold, part of the pilot oil that had been acting on the spool is forced across orifice (15) through passage (16) or across orifice (17), back to tank through drain (20).

NOTE: If the machine is turning while moving, it will continue moving in the radius of the turn. Releasing the STIC control lever will not return the machine to the straight ahead travel position.

Schematic for the Steering Control Valve
(2) Inlet. (3) Shuttle valve. (4) Port to tank. (5) Flow control valve. (6) Passage. (7) Relief valve. (8) Passage. (9) Return passage. (11) Orifice. (12) Passage from left neutralizer. (13) Spool. (14) Passage from right neutralizer. (15) Metering orifice. (16) Passage. (17) Passage. (18) Port for left turn. (19) Port for right turn. (20) Metering orifices. (21) Spring.

For example, a left turn is made and pilot oil flows through passage (12) into chamber (10). This increased pilot pressure on the left side of spool (13) causes the spool to move to the right.

When the STIC control lever is released, pilot oil flow to the left side of the spool stops. Oil in chamber (10) must be removed before the spool can return to the HOLD position. Spring (21) force causes the spool to move to the left when pilot oil pressure is removed from the left side of the spool. As the spool moves, oil in chamber (10) flows through metering orifice (15) through passage (16) into passage (17). The oil flows through the passage to the spring end of the spool.

When the steering control valve is in the HOLD position, oil flow through the valve is blocked by spool (13). This causes inlet (2) oil pressure to increase.

The increase of inlet oil pressure is felt at flow control valve (5). The oil pressure overcomes the force of the valve spring and causes valve (5) to move to the right. Oil now can flow through the openings in the flow control valve and port (4).

While in the HOLD position, the valve spool blocks the flow of steering oil to the cylinders. This holds the machine in the turn position where the STIC control lever last placed it.

The pressure of the oil in blocked outlets (18) and (19) is felt through passages (6) and (8) and also against pilot relief valve (7). If an outside force (for example, a tire strikes a large rock or hole) tries to turn the machine while the valve spool is in the HOLD position, the increase in pressure will open relief valve (7). The relief valve will not allow pressure to rise above the 17 235 ± 345 kPa (2500 ± 50 psi) setting.

RIGHT TURN Position

Steering Control Valve in the RIGHT TURN Position
(1) Alternate pilot oil port. (2) Inlet. (3) Shuttle valve. (4) Port to tank. (5) Flow control valve. (6) Passage. (7) Relief valve. (8) Passage. (9) Return passage. (10) Chamber. (11) Orifice. (12) Passage from left neutralizer. (13) Spool. (14) Passage from right neutralizer. (15) Orifice. (16) Passage. (17) Orifice. (18) Port for left turn. (19) Port for right turn. (20) Drain. (21) Spring.

When the STIC control lever is moved to the right, pilot oil is sent through the right neutralizer valve to passage (14). The oil flows into the chamber for spring (21).

The pressure of the oil in the spring chamber acts against the right side of spool (13) and moves the spool to the left. The amount of spool movement is controlled by how far the STIC control lever is moved to the right.

The oil from chamber (10) flows out passage (12) through the left neutralizer valve, through the dual pilot check valve, back through the STIC control valve to the hydraulic tank.

With the spool moved to the left, oil from the steering pump flows from inlet (2), through slots in the spool, into port (19). This oil flows to the head end of the left steering cylinder and the rod end of the right cylinder. This causes the machine to turn to the right.

When oil enters port (19), the pressure of the oil moves shuttle valve (3) up. Oil also flows through passage (6) into the spring chamber for flow control valve (5). The oil acts against the right side of the flow control valve and also against relief valve (7).

If an outside force prevents the machine from turning, the pressure in port (19) increases. The pressure acts against flow control valve (5) causing it to move to the left. This allows more oil to flow to the cylinders.

Steering Control Valve with the Relief Valve in the OPEN Position
(3) Shuttle valve. (5) Flow control valve. (6) Passage. (7) Relief valve. (11) Orifice.

If the pressure rises above relief valve (7) setting, the relief valve opens. When the relief valve opens oil flows through passage (6) past the valve.

The flow of oil past orifice (11) causes a lower pressure in the spring chamber for flow control valve (5). The pressure of the oil in inlet port (2) can now move the flow control valve to the right. When the valve moves to the right, oil flows from the inlet port through the holes in the flow control valve back to the hydraulic tank.

This releases the pressure in the circuit. When the outside force is removed and pressure reduced to relief valve setting, flow control valve (5) and relief valve (7) move back to their normal positions.

Return oil from the cylinders enters port (18). Then the oil flows into passage (9) and out port (4) back to the hydraulic tank.

LEFT TURN Position

Steering Control Valve in the LEFT TURN Position
(1) Alternate pilot oil port. (2) Inlet. (3) Shuttle valve. (4) Port to tank. (5) Flow control valve. (6) Passage. (7) Relief valve. (8) Passage. (9) Return passage. (10) Chamber. (11) Orifice. (12) Passage from left neutralizer. (13) Spool. (14) Passage from right neutralizer. (15) Orifice. (16) Passage. (17) Orifice. (18) Port for left turn. (19) Port for right turn. (20) Drain. (21) Spring.

Control valve operation for a left turn is similar to that for a right turn. When the STIC control lever is moved to the left, pilot oil is sent through the right neutralizer valve to passage (12).

The pressure of the oil acts against the left side of spool (13), overcomes the force of spring (21) and moves the spool to the right. The amount of spool movement is controlled by how far the STIC control lever is moved to the left.

The oil from the chamber for spring (21) flows out passage (14) through the right neutralizer valve, through the dual pilot check valve, back through the STIC control valve to the hydraulic tank.

With the spool moved to the right, oil from the steering pump flows from inlet (2), through slots in the spool, into port (18). This oil flows to the head end of the right steering cylinder and the rod end of the left cylinder. This causes the machine to turn to the left.

When oil enters port (18), the pressure of the oil moves shuttle valve (3) down. Oil also flows through passage (6) into the spring chamber for flow control valve (5). The oil acts against the right side of the flow control valve and also against relief valve (7).

The remainder of the relief valve and flow control valve operation during a left turn is the same as during a right turn.

Secondary Steering System

SMCS Code: 4300-SE

Schematic for the Steering Hydraulic System (STIC Steer Machines)
(1) Steering cylinders. (2) Secondary steering pump. (3) Secondary steering diverter valve. (4) Crossline relief valves. (5) Steering control valve. (6) Check valves. (7) Oil cooler. (8) Left neutralizer valve. (9) Right neutralizer valve (10) Pilot control valve. (11) Pilot oil pressure reducing valve. (12) Duel pilot check valve. (13) Brake and pilot pump. (14) Steering pump. (15) Vacuum breaker/relief valve. (16) Selector and pressure control valve. (17) Steering secondary lockout valve (door neutralizer). (18) Hydraulic tank group. (19) Hydraulic oil filter group. (20) Manifolds. (AA) Pressure test point for steering system.

The purpose of the optional secondary steering system is to provide an oil supply for the steering system if there is a failure of the primary pump system or if the engine stops while the machine is moving. It also adds oil to the steering pump flow when the engine rpm is less than 2000 ± 40 rpm and the machine is moving.

Location of the Secondary Steering Pump
(2) Secondary steering pump.

Location of the Secondary Steering Diverter Valve
(3) Secondary steering diverter valve.

The main components of the secondary steering system are secondary steering pump (2) and secondary steering diverter valve (3).

The secondary steering pump is mounted on the front of the transmission, attached to the transmission output transfer gears. The secondary steering diverter valve is mounted on the right side of the transmission. The pump is a ground speed driven pump that turns as long as the machine is moving.

With the engine running, primary steering pump (14) sends oil to secondary steering diverter valve (3). The oil flows through the secondary steering diverter valve to steering control valve (5).

When the machine starts to move, secondary steering pump (2) also starts to turn. As the pump turns it draws oil from hydraulic tank (18) and sends it to secondary steering diverter valve (3).

When the engine rpm is less than 2000 ± 40 rpm, oil from the secondary steering pump is combined with oil from the primary steering pump in secondary steering diverter valve (3). This combined oil flows into steering control valve (5).

As the machine moves and engine rpm rises above 2000 ± 40 rpm, the secondary steering diverter valve sends secondary steering pump oil back to the hydraulic tank. The primary steering pump now provides all of the oil to the steering control valve. If, under this condition, there is a primary steering pump failure or the engine stops, the secondary steering diverter valve will route secondary steering pump oil to the steering control valve.

Secondary Steering Diverter Valve

SMCS Code: 4339

Diverter Valve Cutaway (Engine at Low Idle and Machine Stopped)
(1) Diverter spool. (2) Return passage to hydraulic tank. (3) Passage. (4) Spring. (5) Outlet to steering control valve. (6) Passage. (7) Orifice. (8) Check valve. (9) Passage. (10) Inlet from primary steering pump section. (11) Check valve. (12) Supply passage for secondary steering pump. (13) Spring. (14) Reversing spool. (15) Passage to left end of reversing spool. (16) Passage. (17) Passage. (18) Passage to right end of reversing spool.

The main components of the diverter valve are; diverter spool (1), check valves (8) and (11) and reversing spool (14).

When the engine is running, the oil from the primary steering pump flows through inlet (10) and orifice (7) to check valve (8). The force of the oil opens the check valve. The oil flows past the check valve and through outlet (5) to the steering control valve. Check valve (11) will not allow primary oil to flow to passage (3).

The pressure of the oil before orifice (7) is more than the pressure of the oil after the orifice. These pressures are also felt through passages (9) and (6) respectively.

The oil before orifice (7) flows through passage (9) to the left side of diverter spool (1). The pressure of the oil after orifice (7) is the same as the pressure of the oil to the right end of diverter spool (1).

Schematic for the Diverter Valve
(1) Diverter spool. (2) Return passage to hydraulic tank. (3) Passage. (4) Spring. (5) Outlet to steering control valve. (6) Passage. (7) Orifice. (8) Check valve. (9) Passage. (10) Inlet from primary steering pump section. (11) Check valve. (12) Supply passage for secondary steering pump. (13) Spring (14) Reversing spool. (15) Passage to left end of reversing spool. (16) Passage. (17) Passage. (18) Passage to right end of reversing spool.

As the engine rpm increases, the flow from the primary steering pump also increases. Due to the increased flow past orifice (7), there is an increase in the difference of the oil pressure before and after the orifice.

When the force of th eoil on the left end of the spool is more than the total force of th eoil and spring on the right end, the diverter spool will move to the right. This takes place when the engine rpm is 2000 ± 40 rpm.

There is no oil is sent from the secondary steering pump until the machine moves. When the machine moves, the pump is turned by the output transfer gears. Oil from the hydraulic tank is supplied to the secondary steering pump through passage (12). Oil flows from the hydraulic tank through passage (12), to the reversing spool.

Diverter Valve Cutaway (Engine Below 2000 ± 40 rpm and Machine in Forward Motion)
(1) Diverter spool. (2) Return passage to hydraulic tank. (3) Passage. (4) Spring. (5) Outlet to steering control valve. (6) Passage. (7) Orifice. (8) Check valve. (9) Passage. (10) Inlet from primary steering pump section. (11) Check valve. (12) Supply passage for secondary steering pump. (13) Spring. (14) Reversing spool. (15) Passage to left end of reversing spool. (16) Passage. (17) Passage. (18) Passage to right end of reversing spool.

If the engine rpm is below 2000 ± 40 rpm, the diverter spool will be to the left. Oil flow past the diverter spool is stopped. The pressure of the oil in passage (3) increases until check valve (11) opens. This lets the oil from the secondary pump flow past check valve (11) to check valve (8). The oil then flows together with the oil from the primary system and goes through outlet (5). This combined flow of oil then goes to the steering control valve.

If the engine rpm is above 2000 ± 40, the diverter spool will be to the right. The oil from the secondary pump flows into passage (3) The oil flows around spool (1), into passage (2) and back to the hydraulic tank.

Diverter Valve Cutaway (Engine Above 2000 ± 40 rpm and Machine in Forward Motion)
(1) Diverter spool. (2) Return passage to hydraulic tank. (3) Passage. (5) Outlet to steering control valve. (6) Passage. (7) Orifice. (8) Check valve. (9) Passage. (10) Inlet from primary steering pump section. (11) Check valve. (12) Supply passage for secondary steering pump. (13) Spring. (14) Reversing spool. (15) Passage to left end of reversing spool. (16) Passage. (17) Passage. (18) Passage to right end of reversing spool.

Only the primary pump flow is sent to the steering control valve through outlet (5). Check valve (11) will not let the primary oil flow into passage (3).

If there is a failure of the primary steering pump, or if the engine stops, there will be a loss of primary oil flow. Diverter spool (1) will move to the left. As long as the machine moves, the flow from the secondary steering pump will provide the oil for the steering operation.

The oil will flow through passage (3), past valve (11) and through outlet (5). Check valve (8) will prevent the loss of flow through inlet (10) and the stopped primary pump.

When the machine moves in a reverse direction, the secondary steering pump turns in the opposite direction. The pressure oil from the pump is sent through passages (16) and (15) to the left end of the reversing spool. This causes the spool to move to the right. The pressure oil can then flow through passage (16) into passage (3). The rest of the oil flow is the same as when the machine moves forward.

Steering System (Wheel Steer)

SMCS Code: 4300

Schematic for the Steering Hydraulic System (Wheel Steer Machines)
(1) Steering cylinders. (2) Crossline relief valves. (3) Steering control valve. (4) Secondary steering pump (if equipped). (5) Secondary steering diverter valve (if equipped). (6) Oil cooler. (7) Left neutralizer valve. (8) Right neutralizer valve. (9) Steering pump. (10) Steering metering pump. (11) Hydraulic filter group. (12) Hydraulic tank group. (AA) Steering system pressure tap.

The following component information is necessary for machines that are equipped with wheel steering. All other components remain the same as the STIC control system.

The wheel steering hydraulic system is made up of two basic circuits; the pilot circuit and the high pressure circuit.

The pilot circuit controls the movement of the spool in steering control valve (3). The components of the pilot circuit are steering metering pump (10), left and right neutralizer valves (7) and (8) and various lines.

Location of the steering metering pump
(10) Steering metering pump (behind dash cover).

Pump oil from control valve (3) is always available at steering metering pump (10). The steering metering pump is a small hydraulic pump that is used as a metering and directional control valve. It sends pilot oil through one of the neutralizer valves when the steering wheel is turned.

The neutralizer valve stops the flow of pilot oil when the machine is turned completely to the right or left. If the machine is not turned completely, the pilot oil will flow through the neutralizer valve to the respective end of the control valve spool. The oil then flows across the metering orifices in the valve spool. The flow across the orifices causes the spool to move.

The high pressure circuit provides the force needed to turn the machine. The components of the high pressure circuit are hydraulic tank (12), steering pump (9), steering control valve (3), crossline relief valves (2), steering cylinders (1), oil cooler (6), hydraulic filter group (11) and various lines.

The oil for the steering system is sent from steering pump (9) to steering control valve (3). If the pilot oil has moved the valve spool to either the right or left turn position, the oil from the steering pump will flow to steering cylinders (1). The pressure of this oil in the steering cylinders causes the machine to turn.

Return oil from neutralizer valves (7) and (8) and steering metering pump (10) flows back to hydraulic tank (12). Return oil from steering cylinders (1) flows through steering control valve (3), oil cooler (6), filter group (11) and back to hydraulic tank (12).

NOTE: The steering metering pump will not provide manual steering when the engine is stopped. Steering with a dead (stopped) engine can be done only when the secondary steering system is installed.

Steering Metering Pump

SMCS Code: 4312

Steering Metering Pump
(1) Spool. (2) Sleeve. (3) Outlet (to tank). (4) Inlet (for pump oil). (5) Internal pump gear. (6) External pump gear. (7) Centering springs. (8) Pin. (9) Left turn port. (10) Right turn port. (11) Body. (12) Drive. (A) Control section. (B) Metering section.

The steering metering pump has two main sections; control section (A), and pump or metering section (B). These two sections work together to send pilot oil to the steering control valve. The steering wheel is connected to spool (1) by a shaft assembly and splines.

Oil from the steering pump flows through inlet (4) into the control section of the steering metering pump. When the steering wheel is turned, the control section sends the oil to and from the metering section and also to and from the steering control valve.

The metering section is a small hydraulic pump. It controls (meters) the pilot oil that flows to the steering control valve. As the steering wheel is turned faster, there is an increase in the flow of pilot oil to the steering control valve.

The increased flow causes the steering control valve spool to move farther. As the spool moves farther, more oil can flow from the steering pump to the steering cylinders. This results in a faster turn.

Oil Flow

The control section of the steering metering pump is a closed center type valve. When the steering wheel is stationary (NEUTRAL), oil flow is blocked by spool (1). Pump oil can not flow through inlet (4) until the steering wheel is turned.

When the steering wheel is turned, spool (1) turns a small amount and springs (7) are compressed. As springs (7) compress, sleeve (2) starts to turn. As long as the steering wheel is turned, the spool and sleeve both turn as a unit, but they turn a few degrees apart.

When the spool and sleeve are a few degrees apart, oil passages are opened between them. This allows the pump oil from inlet (4) to flow through passages in body (11) to the metering section.

Pump Gears in the Metering Section
(5) Internal pump gear. (6) External pump gear. (8) Pin. (12) Drive.

When the steering wheel is turned, pin (8) turns with the sleeve and causes drive (12) to turn also. The drive causes gear (5) to rotate inside gear (6). The rotation of the gear sends a metered flow of pilot oil back through body (11).

This oil flows to port (9) or (10) and then on to the neutralizer valve. Port (9) or (10) that is not used for pilot oil, is used for return oil from the other end of the control valve spool.

When steering wheel rotation is stopped, centering springs (7) move sleeve (2) back in alignment with spool (1) (NEUTRAL position). This will close passages between the metering and control sections and the steering metering pump will be in the NEUTRAL position.

Steering Neutralizer Valve (Wheel Steer)

SMCS Code: 4330

Neutralizer Valve in the CLOSED Position
(1) Striker. (2) Inlet. (3) Ball check valve. (4) Outlet. (5) Stem. (6) Spring.

The neutralizer valve stops the flow of pilot oil to the steering control valve at the end of a complete turn. This stops the steering action before the machine turns against the frame stops.

Striker (1) for each valve is mounted on the front frame. Both of the neutralizer valves are mounted on the rear frame. The right and left neutralizer valves and strikers are identical.

Schematic for the Neutralizer Valves
(1) Striker. (2) Inlet. (3) Ball check valve. (4) Outlet. (5) Stem. (6) Spring. (7) Left neutralizer valve. (8) Oil line. (9) Oil line. (10) Right neutralizer valve. (11) Drain line. (12) Pilot oil line. (13) Pilot oil line.

Pilot oil flows from the steering metering pump to either the right or left neutralizer valves before flowing to the steering control valve. Oil flows from the steering metering pump through line (12) or (13) into neutralizer valve (7) or (10) through inlet port (2). Then the oil flows around stem (5) and through outlet port (4) into line (8) or (9). Then the oil flows to the steering control valve.

When the steering wheel is turned to the right turn position, and the machine is turned as far right as it can turn, striker (1) comes in contact with stem (5) of the right neutralizer valve. The striker forces the stem to compress spring (6) and moves the stem until pilot oil can not flow from port (2) to port (4). This stops the flow of pilot oil through line (9).

When the flow of pilot oil stops acting on the spool in the steering control valve, the control valve spool returns to the HOLD position. This causes the steering action of the machine to stop.

When the steering wheel is turned back to the left return oil from the end of the steering control valve spool flows through line (9) into port (4) of the right neutralizer valve. Because stem (5) has oil flow from port (2) to port (4) blocked, the oil forces ball check (3) to the right. The oil now flows out port (2) through line (13) back to the steering metering pump. The machine begins to turn to the left.

As the machine moves to the left a small amount, striker (1) will move away from stem (5). Spring (6) tension acts against stem (5) and moves it back into the open position. This allows the pilot oil to flow around the stem again, and ball check valve (3) closes.

The left neutralizer valve operates in exactly the same manner as the right neutralizer valve.

Steering Control Valve (Wheel Steer)

SMCS Code: 4307

HOLD Position

Steering Control Valve in the HOLD Position
(1) Check valve. (2) Inlet. (3) Ball resolver valve. (4) Outlet to tank. (5) Flow control valve. (6) Passage. (7) Relief valve. (8) Passage. (9) Return passage. (10) Chamber. (11) Orifice. (12) Passage (from left neutralizer valve). (13) Spool. (14) Passage (from right neutralizer valve). (15) Metering orifices. (16) Passage. (17) Passage. (18) Outlet for left turn. (19) Outlet for right turn. (20) Metering orifices. (21) Spring.

In the HOLD position, the valve spool also blocks (stops) the oil in the lines to the cylinders. This holds the machine in the turned position where the steering wheel was stopped.

NOTE: A very small amount of oil can still flow from outlets (18) and (19), through a bleed slot and then to return passage (9).

The pressure of the oil in the blocked outlets (18) and (19) is felt through passages (8) and (6) and against relief valve (7). If an outside force tries to turn the machine when the valve spool is in the HOLD position, the increase in pressure will open relief valve (7).

The flow of pilot oil to either end of valve spool (13) is stopped when; (a) rotation of the steering wheel is stopped, or (b) the neutralizer valve stops the flow after a complete turn has been made. With no pilot oil flow against either end of the valve spool, spring (21) will keep the spool in its HOLD position.

When the steering control valve is in its HOLD position, the oil from the steering pump is stopped by the valve spool. The pressure increases in inlet passage (2). This pressure increase moves flow control valve (5). The flow control valve moves until oil can flow through it to outlet (4).

The pressure in the lines will not go higher than the relief valve setting of 17 235 ± 345 kPa (2500 ± 50 psi). When the pilot flow to one end of the spool stops, part of the oil on that end of the spool must be removed before the valve spool can return to the HOLD position. To do this, part of the oil is pushed, by the force of spring (21), to the opposite end of the spool. The spool can then move to its HOLD position.

As an example, a left turn is made and pilot oil flows into chamber (10) through passage (12). The pressure drop (reduction) across orifices (15) causes spool (13) to move to the right. When the pilot flow stops, part of the oil in chamber (10) must be removed so that the spool can move to the HOLD position. The force of spring (21) causes the spool to move to the left. As the spool moves, oil that is pushed from chamber (10) flows through metering orifices (15). The oil flows through passage (17) to the spring end of spool (13). The spool movement goes on until the orifices are blocked and flow through them is stopped. This movement of the spool stops the flow of pressure oil to the steering cylinders.

Right Turn Position

Steering Control Valve in the RIGHT TURN Position
(1) Check valve. (2) Inlet. (3) Ball resolver valve. (4) Outlet to tank. (5) Flow control valve. (6) Passage. (7) Relief valve. (8) Passage. (9) Return passage. (10) Chamber. (11) Orifice. (12) Passage (from left neutralizer valve). (13) Spool. (14) Passage (from right neutralizer valve). (15) Metering orifices. (16) Passage. (17) Passage. (18) Outlet for left turn. (19) Outlet for right turn. (20) Metering orifices. (21) Spring.

When the steering wheel is turned to the right, pilot oil is sent through the right neutralizer valve to passage (14). The oil flows into the chamber for spring (21). There is a pressure drop (reduction) across metering orifices (20). This pressure drop moves the spool to the left. The amount of spool movement is controlled by the rotation of the steering wheel. If there is a slow rotation of the steering wheel, there will be a low volume of oil and less spool movement. A slow turn is the result. A faster rotation of the steering wheel gives a larger volume of pilot oil. This results in more spool movement and a faster turn.

Pilot oil flows from the spring chamber across metering orifices (20). This oil flows through passage (16) to chamber (10). From the chamber, the oil goes through passage (12), through the left neutralizer valve to the steering metering pump. The steering metering pump lets the oil return to the hydraulic tank.

With the spool moved to the left, oil from the steering pump can flow from inlet (2), through slots in the spool, into outlet (19). This oil flows to the head end of the left steering cylinder, and the rod end of the right steering cylinder.

The pressure of the oil in the cylinders extends the left cylinder rod and retracts the right cylinder rod. This causes the machine to turn to the right.

Return oil from the cylinders enters outlet (18). It flows into passage (9) and then through outlet (4).

When the oil enters outlet (19), the pressure moves ball resolver valve (3). The pressure of oil to the cylinders is felt through passage (6), against relief valve (7) and flow control valve (5).

Steering Control Valve with the Relief Valve in the OPEN Position
(3) Ball resolver valve. (5) Flow control valve. (6) Passage. (7) Relief valve. (11) Orifice.

If an outside force prevents the machine from turning, the pressure in outlet (19) will increase. This pressure increase is also felt against the relief valve and flow control valve. The pressure against flow control valve (5) causes it to move to the left. This lets more oil flow to the cylinders. If the pressure rises above the relief valve setting, the relief valve will open.

When the relief valve opens, oil flows through passage (6) and past the relief valve. The flow of oil past orifice (11) causes a lower pressure in the chamber for the flow control spring. This lets the pressure of the oil in the inlet passage move flow control valve (5).

Oil from inlet (2) can flow through the holes in the flow control valve, which now works as a dump valve. This releases the extra pressure from the circuit. When the outside force is gone and the pressure is reduced, the flow control valve and relief valve return to their normal positions.

Left Turn Position

Pump oil from inlet (2) flows through the slots in spool (13) to outlet (18). This oil flows to the head end of the right steering cylinder and to the rod end of the left steering cylinder.

The pressure of the oil in the cylinders extends the right cylinder rod and retracts the left cylinder rod. This causes the machine to turn to the left.

When the valve spool is in the left turn position, the pressure of the oil to the cylinders is felt through passage (8) and across the ball resolver valve. This same pressure is felt through passage (6) and at relief valve (7). The remainder of the relief valve operation is the same for the LEFT TURN position and the RIGHT TURN position.

Steering System (Reversible Steering)

SMCS Code: 4300-QR

Schematic for the Steering Hydraulic System (Wheel Steer Machines)
(1) Steering cylinders. (2) Crossline relief valves. (3) Steering control valve. (4) Secondary steering pump (if equipped). (5) Secondary steering diverter valve (if equipped). (6) Oil cooler. (7) Left neutralizer valve. (8) Right neutralizer valve. (9) Steering pump. (10) Reversible steering control valve. (11) Steering metering pump. (12) Hydraulic filter group. (13) Hydraulic tank group. (AA) Steering system pressure tap.

Reversible Steering Control Valve (Typical)
(10) Reversible steering control valve.

The reversible steering system changes the direction the steering wheel must be rotated to make a turn when the machine is driven in a reverse direction. Normal steering wheel rotation occurs when the machine is driven in a forward direction.

This arrangement consists of the standard wheel steering system and a solenoid operated hydraulic control valve.

This valve is fitted between the pilot lines from the steering metering pump and the steering neutralizer valves. The pilot lines from reversible steering control valve (10) to neutralizer valves (7) and (8) are reversed because of the configuration of the reversible steering control valve. When the transmission is in neutral or forward speed, oil flow to the steering control valve is the same as a standard machine. When the transmission is shifted to a reverse speed, the solenoid valve reverses the pilot oil flow to the steering control valve, reversing the direction of the steering.

When the steering wheel is rotated clockwise, with the transmission in neutral or a forward speed, Steering metering pump (11) sends pilot oil through reversible steering control valve (10) to right neutralizer valve (8). If the neutralizer valve spool is open, then pilot oil will flow to the right side of the steering control valve spool. The pilot oil will move the valve spool, directing oil to the steering cylinders to turn the machine to the right.

When the transmission control lever is moved to the reverse position, the electronic transmission control sends power to energize reversible steering control valve (10). Now pilot flow to the steering control valve is reversed.

When the steering wheel is rotated clockwise, steering metering pump (11) sends pilot oil through reversible steering control valve (10). The direction of flow is changed and sent to left neutralizer valve (7). If the neutralizer valve spool is open, then pilot oil will flow to the left side of the steering control valve spool. The pilot oil will move the valve spool, directing oil to the steering cylinders to turn the machine to the left.

When the transmission control lever is moved to a position other than reverse, the power supply to reversible steering control valve (10) is interrupted. The spool in the steering control valve is returned to the normal position and the steering function operates as standard.