PRIMARY POWERTRAIN CONTINUED
Relief Valve (Main)
Pump supply oil enters the main relief valve through the passage (Figure 6, Item 1) and enters a hole in the spool
(Figure 6, Item 5) flowing through an internal passage in the spool. The pressure of this oil is felt in the slug
chamber (Figure 6, Item 6).
The oil acts on the slug (Figure 6, Item 7). The slug cannot move to the left. The oil pressure will push the spool
(Figure 6, Item 5) to the right. When the oil pressure in the slug chamber (Figure 6, Item 6) exceeds the force of the
spring (Figure 6, Item 4), the spool moves to the right.
When the spool moves to the right, pump oil is allowed to exit through the passage (Figure 6, Item 2) and is used
to lubricate the transmission.
When the pressure in the passage (Figure 6, Item 1) is no longer high enough to overcome the force of the spring
(Figure 6, Item 4), the spool (Figure 6, Item 5) shifts back to the left.
The pressure setting of the main relief valve may be adjusted with the adjustment screw (Figure 6, Item 3).
Figure 6. Relief Valve (Main).
The accumulator for the powertrain is located on top of the bevel gear case at the back of the machine.
The accumulator stores potential energy by accumulating a quantity of pressurized powertrain oil, which is stored
in an accumulator cylinder. The accumulator is charged to 250 psi (1,724 kPa) with dry nitrogen.
The pressurized powertrain oil enters the accumulator and creates pressure. Energy is stored within the
accumulator as the gas behind the cylinder inside the accumulator is compressed by the powertrain oil. The
accumulator supplements powertrain oil flow in low flow conditions.
Figure 7. Accumulator.