Theory of Operation
control pressure sensors increases because pilot oil
When the propel speed switch (A) is in slow speed,
control signals from front and rear pump control valves
the propel speed change solenoid valve (N) coil is
de-energized. The speed selector valve spools (E) are
Rear and front pump pressure sensors (K) are
open to return through the solenoid valve. The propel
sensing low supply oil delivery pressure.
motors (D and F) are at maximum displacement
causing the machine to travel at slow speed.
When the electrical signals are received at the engine
and pump controller (O), the controller sends an
The propel speed goes to fast with the following
electrical signal to energize the solenoid valve (N) coil.
The pilot oil pressure signal shifts the speed change
valve spool (E) causing the motor to go to minimum
Propel speed switch is at fast speed.
displacement and the machine to travel at fast speed.
Propel pressure switch (H) in closed.
(See Propel Motor Fast Speed Operation in this
Dig pressure switch (G) is open.
Electrical signal for front (J) and rear (C) pump