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| Illustration 1 | g00562767 |
Selector The selector is shown in NEUTRAL position with a running engine. (3) Priority reduction valve (4) Neutralizer valve (5) Rotary selector spool (12) Accumulator | |
| Selector | ||
| Item | Component | Operation of Component |
| (3) | Priority reduction valve | This component controls the pressure of the pilot oil that is available to rotary selector spool (5). |
| (4) | Neutralizer valve | This component stops the flow of the pilot oil to rotary selector spool (5) when the machine is started in any speed position except NEUTRAL. |
| (5) | Rotary selector spool | This component sends pilot oil to the pressure control. The pressure control determines the clutches that are engaged. The pressure control determines the speed of the transmission. |
| (12) | Accumulator | This component assists in automatic modulation after inching the machine. |
The selector is made up of the following four components:
- Priority reduction valve (3)
- Neutralizer valve (4)
- Rotary selector spool (5)
- Accumulator (12)
Table 1 shows the function (operation) of each component.
Priority Reduction Valve
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| Illustration 2 | g00584948 |
Selector The selector is shown in NEUTRAL position with a running engine. (1) Passage to rotary actuator (2) Passage from pump (3) Priority reduction valve (4) Neutralizer valve (5) Rotary selector spool (7) Chamber (pressure) (8) Passage to relief valve (9) Chamber (10) Passage for pump oil (14) Passage to pressure control | |
At the selector, the oil from the transmission pump flows to several different places. The oil comes in passage (2). Some of the oil flows through passage (1) to the rotary actuator.
Some of the oil flows through passage (8) to the relief valve.
The remainder of the pump oil flows to priority reduction valve (3). The oil flows through an orifice that is in priority reduction valve (3). The oil opens a check valve (poppet). The oil then flows to the upper end of priority reduction valve (3) .
The oil pressure will cause the valve to move down against the force of the valve spring, as the pressure increases. The pressure of the oil from priority reduction valve (3) that flows to neutralizer valve (4) is controlled by the priority reduction valve.
When the neutralizer valve moves down, the oil flows to chamber (7) in rotary selector spool (5). The oil can then flow to the pressure control. This pressure oil is the "pilot oil" that controls the movement of the selector pistons in the pressure control.
As priority reduction valve (3) moves down, the priority reduction valve also permits pump oil in passage (2) to flow out of passage (10). Some of the oil flows through passage (14) to the pressure contol and the manual modulation valve (inching).
The oil is used to fill the clutches in the transmission. Some of the oil also flows to rotary selector spool (5). This oil is used to activate neutralizer valve (4) .
When the rotary selector spool is in NEUTRAL position, the spool allows oil flow to chamber (9). This causes neutralizer valve (4) to move down. Pilot oil is now free to flow to chamber (7) of rotary selector spool (5) .
The pressure setting of the priority reduction valve is approximately 1725 ± 35 kPa (250 ± 5 psi). This pressure can be changed by removing or adding shims.
Neutralizer Valve
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| Illustration 3 | g00584970 |
Selector The selector is shown in NEUTRAL position with a running engine. (4) Neutralizer valve (5) Rotary selector spool (7) Chamber (pressure) (9) Chamber (10) Passage for pump oil (11) Chamber (drain) | |
Neutralizer valve (4) does not permit movement of the machine if the engine is started with the transmission speed selector lever out of NEUTRAL position.
When the engine is started with the transmission in NEUTRAL position, pressure oil from passage (10) flows to rotary selector spool (5), and then to chamber (9) .
The pressure oil in chamber (9) flows through an internal passage that is in the neutral valve spool. The pressure oil in chamber (9) flows through an orifice that is in the check valve seat, and then to a cavity at the upper end of neutralizer valve (4) .
The pressure that is in the cavity will cause neutralizer valve (4) to move down against the force of the valve spring. This allows pilot oil to flow around the neutralizer valve to chamber (7) of the rotary selector spool. The clutches can now be engaged in the transmission.
As neutralizer valve (4) moves down, pilot oil can then flow through the orifice in the check valve seat, and then to the upper end of the valve. The valve is now held in the position by the pressure of the pilot oil.
When rotary selector spool (5) is moved from NEUTRAL position, pressure oil from passage (10) cannot flow to chamber (9). Chamber (9) is now open to chamber (11) because of the position of the rotary selector spool.
When the engine is started with the transmission in any speed position except NEUTRAL, the following condition is present:
- The position of rotary selector spool (5) blocks the flow of pump oil to chamber (9) .
Neutralizer valve (4) cannot move down when the pump oil is blocked at chamber (9). Pilot oil will not be available at chamber (7) in rotary selector spool (5). If the pilot oil is not available to chamber (7), the pilot oil will not be available to the selector pistons of the pressure control. As a result of the blocked pilot oil, the clutches in the transmission cannot engage.
Rotary Selector Spool
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| Illustration 4 | g00584971 |
Selector The selector is shown in NEUTRAL position with a running engine. (4) Neutralizer valve (5) Rotary selector spool (7) Chamber (pressure) (9) Chamber (11) Chamber (drain) | |
The flow of pilot oil is regulated by rotary selector spool (5). This component determines the selector pistons that get pilot oil and the selector pistons that are drained.
The orifices in the spool provide the correct sequence for the engagement of the clutches.
The rotary actuator is connected to the upper end of the rotary selector spool. The rotary actuator hydraulically turns the rotary selector spool.
There is pilot oil inside chamber (7) of rotary selector spool (5). Because of the position of the spool, oil will be sent through a passage to the pressure control. The oil will flow to the selector piston. This will cause the piston to move.
The movement of the piston causes a clutch or clutches to engage in the transmission. There is a screen filter in chamber (7). The filter will keep foreign material out of the pressure control.
At the same time, pressure oil is sent into chamber (11). This pressure oil is sent to chamber (11) by the transmission clutches that are being disengaged. This pressure oil comes from each selector piston of the transmission clutches. Chamber (11) allows the oil flow back to the reservoir (drain).
In the NEUTRAL position, rotary selector spool (5) sends pump oil to chamber (9). This pump oil will move neutralizer valve (4). In all other speed positions, chamber (9) is blocked from the pump oil. Chamber (9) is then open to chamber (11) .
Accumulator
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| Illustration 5 | g00584972 |
Selector The selector is shown in NEUTRAL position with a running engine. (12) Accumulator | |
Accumulator (12) assists the manual modulation valve in modulating transmission clutch pressure. Accumulator (12) assists the manual modulation valve from 240 kPa (35 psi) to full pressure after manual modulation. Accumulator (12) accepts an extra volume of oil. This oil helps modulate clutch pressure in order to prevent harsh clutch engagement.