Service Manual

Traction Forward
The traction pump is driven by the engine through the
pulley, pump drive belt, and electric clutch. The traction
circuit of the hydraulic system acts essentially as a
closed loop. Taking its suction directly from the return
side of the wheel motors of the traction circuit, the trac-
tion pump supplies oil flow to the wheel motors through
the supply side of the traction circuit.
With the engine running, clutch engaged, and traction
pedal in the neutral position, the traction pump supplies
no flow to the wheel motors. When the traction pedal is
pressed to the forward position, the linkage from the
pedal positions the swash plate in the traction motor so
oil flows out the top port of the pump. Oil flow out of the
top port goes to the wheel motors and turns them in the
forward direction. The 2WD/3WD selector valve allows
flow to the rear wheel in the 3WD position and by–
passes the rear wheel in the 2WD position.
Oil flowing out of the wheel motors returns to the bottom
port of the traction pump and is continuously pumped
out the top port. However
, oil flow out of the rear wheel
motor must pass through the check valve portion of the
PC flow controller before returning to the traction pump.
A small amount of hydraulic oil leaves the traction circuit
through the bi–directional shuttle valve in the front left
wheel motor
. This oil is cooled as it flows through the
cooler and returned to the reservoir.
Filtered hydraulic oil is supplied to the traction circuit
from the charge pump though the lift control valve and
back through the charge circuit check valves. This fil-
tered oil replaces oil losses from flow through the shuttle
valve and small amounts of leakage. The charge pump
and shuttle valve circuits allow for indirect cooling and
filtering of the traction circuit.
In the forward direction, the PC flow controller has a spe-
cial function. When a unit is moving downhill, the opera-
tor will return the traction pedal to the neutral position.
In this situation, the front wheel motors act as hydraulic
pumps and reverse the oil flow through the traction cir-
cuit. The PC flow controller will restrict flow to the rear
motor suf
ficiently, so the reverse flow is by–passed
through the 2WD/3WD selector (check) valve around
the rear wheel motor. This action will prevent a loss of
steering control should the rear motor turn in the reverse
direction. As a result, there is no 3WD in reverse
Hydraulic System Page 4 – 10 Reelmaster 2300–D/2600–D