Service Manual

310-3000 IHT

Figure 1. 310-3000 Hydraulic Schematic

HYDRAULIC SCHEMATIC

Figure 1 provides an illustration of the hydraulic

oil circuit. The oil supply for the hydraulic system

of the 310-3000 IHT is also utilized for the lubri-

cation of the planetary differential drive gears.

The input shaft and pump cylinder block are turned

in one direction only by the engine/drive belt/pul-

ley combination. Output of the oil flow is controlled

by the direction and amount that the swashplate

is angled. As the pump pistons compress they

force the oil to flow through one of two passage-

ways (forward or reverse) in the center section

(or valve body) to the motor cylinder block and

motor shaft. Since the motor has a fixed displace-

ment angle it is forced to turn with the flow of oil.

As the angle of the swashplate is increased the

amount of oil being pumped will increase and

cause a higher RPM output of the motor. Revers-

ing the angle of the pump swashplate will reverse

the direction of oil flow.

During the operation of the transaxle, fluid is “lost”

from the hydraulic loop through leak paths de-

signed into the product for lubrication purposes

(around pistons, under the rotating cylinder

blocks, etc.). This “lost” fluid returns to the trans-

mission housing and must be made up in the

loop. A charge pump is included on the 310-3000

IHT to supply this makeup flow. The make up flow

is controlled (or directed) by the check valves.

Each check valve will either be held opened or

closed (depending upon the direction of vehicle

operation) by the system operating pressure

(closed) or by charge pressure (open) from the

charge pump.

The charge pump maintains a continuous flow of

oil as long as the input shaft is turning. All of the

oil being pulled into the charge pump first must

pass through an internal filter. Any oil not needed

by the transmission for make up flow is