3 - 4
Automatic 2-Speed Switching
Speed range changing is achieved by altering the angle of
the traction motor swash plate. A solenoid operated valve
routes pilot oil to the swash plate adjusting mechanism, as
appropriate, in response to range selection commands.
Low speed Operation
When ‘low speed’ is selected there is no pilot oil pressure at
port D. Spool 186 is pushed upwards by spring 189 and
pressure from port A or B. Oil is released from chamber E
into the motor case via spool 186 and drain H, allowing
swash plate 103 to pivot on fulcrum F to the maximum angle
(O1) up against surface Y of spindle 2. In this swash plate
position the piston stroke volume is maximised to produce
low speed revolution.
High Speed Operation
When ‘high speed’ is selected, pilot pressure greater than 39
bar (569 lbf/in
2
, 40 kgf/cm
2
) is applied to port D where it
overcomes the force of spring 189 and the pressure from
port A or B to push spool 186 down. The pressurised oil at
port C goes via spool 186 into chamber G and thence into
chamber E. Piston 161 pivots swash plate 103 about its
fulcrum F until it contacts surface X of spindle 2. At this
minimum angle (O2) position, the piston stroke volume is
minimised to produce high speed revolution.
Section F Transmission
9803/6410
Section F
3 - 4
Issue 1
Operation
JS01670
JS01680
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