Hydraulic Operation - Manitowoc Grove CD3340B Service Manual

CD3340B/YB4411

Hydraulic Operation

When the Powershift Transmission is operated, multi-disc
clutch packs are pressurized and engaged. The engaged
clutch packs then transfer drive from the engine to the road
wheels (via the torque converter A [Figure 7-3], input shaft H
and the drive shafts).
Different combinations of engaged clutches give four gear
ratios in forward and reverse drive. There must always be
two clutches engaged before the crane will drive: a direction
ratio clutch (i.e., forward low) and a drive clutch (i.e., layshaft
or mainshaft).
Figure 7-3 shows 1st gear reverse selected, therefore, the
two engaged clutches will be reverse low ratio clutch B and
layshaft drive clutch E.
For purpose of this description, clutches not used when 1st
gear reverse is selected are not shown.
Oil from the pump Q is fed through an internal passage by
way of the filter Y to pressure the pressure maintenance
valve R, which maintains a constant pressure to the solenoid
valve adapter blocks S.
The solenoid adapter block houses the solenoid valves,
which are used to divert oil to the clutch packs. When the
solenoids are actuated oil flows through the valves to the
clutch pack.
GROVE
TRANSMISSION AND TORQUE CONVERTER
Excess oil from the maintenance valve flows through the
casing to the torque converter. Oil enters the converter
between the converter hub and stator support, and leaves
between the stator and the input shaft. Pressure in the
converter is controlled by relief valve T which dumps oil from
the converter line back to the sump.
Oil from the torque converter flows out of the transmission
unit to the external oil cooler V. From the cooler, the oil flows
to pipe cluster W (the pipe cluster is only used on earlier
transmissions, on later transmissions oil flow is incorporated
within the casing, which distributes the oil to pass through
the center of all clutches for lubrication purposes).
In neutral the flow of pressurized oil is blocked at the
solenoid valves.
Restrictor orifice X in the feed lines to the solenoid valves
modulates the pressure to the clutches. This ensures a
smooth clutch engagement. Pressure from the clutches not
engaged will vent back to the sump by way of internal
passages and the solenoid spools.
With 1 gear reverse selected valves G and M are
s t
energized. The energized valves cause internal spools to
move, which then divert pressurized oil to clutch packs B and
E by way of internal passages.
The drive from the engine is then transferred by way of the
engaged clutches and gears to the output flange and finally
to the road wheels.
Published 04/07/2015 Control # 569-00
7
7-5