HOW THE UNITS OPERATE (cont)

When either directional clutch is selected the opposite clutch is relieved of pressure and vents back through the direction

selector spool. The same procedure is used in the speed selector.

The direction or speed clutch assembly consists of a drum with internal splines and a bore to receive a hydraulically

actuated piston. The piston is "oil tight" by the use of sealing rings. A steel disc with external splines is inserted into the

drum and rests against the piston. Next, a friction disc with splines at the inner diameter is inserted. Discs are alternated

until the required total is achieved. A heavy back-up plate is then inserted and secured with a snap ring. A Hub with

O.D. splines is inserted into the splines of discs with teeth on the inner diameter The discs and hub are free to increase

in speed or rotate in the opposite direction as long as no pressure is present in that specific clutch.

To engage the clutch, as previously stated, the control valve is placed in the desired position. This allows oil under

pressure to flow from the control valve, through a tube, to a chosen clutch shaft. This shaft has a drilled passageway for

oil under pressure to enter the shaft. Oil pressure sealing rings are located on the clutch shaft. These rings direct oil

under pressure to a desired clutch. Pressure of the oil forces the piston and discs against the heavy back-up plate. The

discs, with teeth on the outer diameter, clamping against discs with teeth on the inner diameter, enables the hub and

clutch shaft to be locked together and allows them to drive as a unit.

There are bleed balls in the clutch piston which allow quick escape for oil when the pressure to the piston is released.

FIG. A