Specifications

Power Train Systems Operation 30
Forward Direction During Inching
When the transmission is in FORWARD (or
REVERSE) during INCHING, the oil flow from the
reservoir, through the pump, filter, torque converter
and oil cooler circuits will be the same as explained in
NEUTRAL position.
Oil will flow from the main relief valve through a
passage, to inching valve (6). Inching valve (6) lets the
operator control the oil pressure to forward clutch (11)
between 280 and 0 kPa (40 and 0 psi), which permits
a partial engagement of the clutch. Through the use of
the inching valve, the lift truck can move slowly while
the engine is at higher speeds. This lets the operator
move the lift truck slowly up to a load while the mast is
raised rapidly.
When the operator pushes the inching pedal part of
the way down, inching plunger (6B) moves out of the
inching valve. This takes away some of the spring
force between plunger (6B) and reducing spool (6A). It
also removes the balance condition between the pump
pressure, at the bottom of spool (6A), and the spring
force. Reducing spool (6A) moves to the right, which
causes a restriction for the pump oil flow. The
pressure drops from 895 kPa (130 psi) to 280 kPa (40
psi). The pressure can drop further depending on the
position of plunger (6A). Pressure reduces as plunger
(6A) is moved out (as the inching pedal is pushed
down).
This reduced pressure flows to selector valve group
(8). The oil will flow through the valve as explained in
forward direction. The reduced (inching) pressure will
flow through a passage to partially engage forward
clutch (11). This reduced pressure permits slippage of
the forward clutch plates and discs. Therefore, the
truck will have an operator controlled movement. The
amount of oil pressure to clutch (11) depends on the
position of inching plunger (6A). As the plunger is
pulled out completely (inching pedal all the way down)
clutch pressure will drop to 0 kPa (0 psi). The forward
clutch will be disengaged at approximately 65.5 kPa
(9.5 psi).