Massey Ferguson 5400 - Issue 1.a
05C02.5
GBA20 Power Shuttle
Operating principle
Forward clutch
When the lever under the steering wheel is in the
Forward position, the relevant solenoid valve is acti-
vated and supplies a pressure that moves piston (28).
This, in turn, compresses the intermediate plates (30)
and the discs (29) against cover (33).
The drive from the engine to the gearbox complies
with the following kinematics:
- input shaft (19) splined to unit (18),
- unit housing (18),
- intermediate plates (30),
- discs (29) compressed by the piston (28),
- hub (27),
- primary shaft (55),
- main unit mainshaft via the input pinion.
Simultaneously, the pressure applied behind the
piston (39) of the braking device drops and the planet
carrier assembly (discs (47), intermediate plates (46)
and epicyclic gear train) rotate freely.
Lubrication
During forward operation, the oil flow from the centre
housing via the pump (14) is directed towards the inter-
mediate plates (30) and the discs (29) via the ports of
the forward clutch unit (18) opened by movement of
piston (28).
At the same time, lubrication of the braking device of
the planet carrier (discs (47) and intermediate plates
(46)) of the reverse clutch is interrupted.
Reverse clutch
When the previously mentioned lever is moved from
the Forward to Reverse position, the solenoid valve
concerned is activated and supplies the piston (39) of
the braking device of the planet carrier. The piston then
presses on plate (43) which compresses discs (47) and
the intermediate plates (46) against the front cover of
the input unit and stops the rotation of the planet
carrier. The drive from the engine is directly trans-
mitted to the cover (33) that is integral with the input
sun gear (53) via splines, without passing through the
discs and intermediate plates of the forward clutch.
Simultaneously, the oil pressure in the piston chamber
(28) drops and frees the discs (29) and intermediate
plates (30).
The input sun gear (53) then drives the double pinion
gears (52) freely mounted on the pins (50) which, in
turn, drive the single pinion gear (59), integral with
primary shaft (55) thus reversing rotation of the output
sun gear (58) splined to the primary shaft (55). The
primary shaft then sends the drive from the engine to
the mainshaft of the main gearbox via the input pinion.
N
OTE: A valve screwed to the top of cover (38) ensures
a small permanent bleed starting from 13 bar to
provide an automatic bleed of the hydraulic supply of
piston (39).
Lubrication
As the piston (39) moves, it operates spools (44) that
act as valves and compress springs (45) via the plate
(43). The spools have a drilled centre channel and radial
ports, allowing oil to flow to the channels in the cover
(38) and the channels in the front cover of the input
unit, thus lubricating the discs (47) and the interme-
diate plates (46). Lubrication of the mechanical parts of
the epicyclic gear train is via the lubricating system of
the input unit.
At the same time, the lubricating oil flow to the discs
(29) and intermediate plates (30) of the forward clutch
is stopped, thus preventing any possible driving of the
discs through a drag effect.
Neutral position
In neutral position, the supply to the solenoid valves is
cut, placing the forward and reverse clutches at rest
and eliminating transmission of the engine drive to the
gearbox.
The oil flow is also interrupted. The pressure in the
circuit opens the valve (1) (Fig. 18) and directs the oil to
the housing.
N
OTE: After replacement of the solenoid valve or its
solenoid, the Power Shuttle hydraulic unit, the power
shuttle unit or one of its component or the transmis-
sion control unit, it is necessary to calibrate the clutch
(see section 11).
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