Service Manual

THEORY OF OPERATION
5xi Series Tractor Hydraulic Service Manual 2 - 9
2
The operator controls the transmission by
moving the control shaft connected to the cam
ring within the pump. With the control shaft in
neutral, or its centered position, no flow is
generated by the pump and, therefore, the motor
portion is at rest.
When the control shaft is moved from neutral in
the “forward” direction, the cam ring in the pump
is moved off center and the pump ball-pistons
create a flow of fluid. The position of the control
shaft/cam ring is infinitely variable and any flow
rate is possible up to maximum cam ring
movement/maximum pump displacement.
Flow created by pump moves to fixed
displacement motor through internal
passageways. Because the motor is a fixed
displacement unit, the motor requires a specific
volume of fluid for it to make one complete
revolution.
(A) Pump
(B) Motor
(C) High Pressure
(D) Low Pressure
When the control shaft is moved from neutral to
“reverse” direction, the cam ring is swung off
center to the opposite side of the pump and the
flow from the pump is “reversed”. This flow is
directed to the other side of the motor causing its
output shaft to rotate in the opposite direction.
The pump input shaft always rotates in one
direction, dictated by the engine, while the motor
output shaft rotates in either direction, depending
on the direction of flow from the pump.
Pump discharge flow is high pressure (dictated
by load) fluid. Flow returned from the motor to
the pump is low (or charge) pressure fluid.
(A) Pump
(B) Motor
(C) Low Pressure
(D) High Pressure
3094-042
0202-003
0202-004