Transmission
9803/3280 Issue 1
Powershift Gearbox
Clutch Operation - Forward, Reverse
The forward and reverse clutch units are very similar in
design and operate in the same way. The following
description refers to one unit and can be applied to either
the forward or reverse clutch units.
The clutch 1 transfers drive from the input shaft A3 to either
gear G1 or gear G2 depending on which of the two clutches
(A1 or A2) is engaged, transferring drive to the mainshaft.
When neither clutch is engaged, neutral is selected.
The clutches are of the wet, multi-plate type.
The clutch housings and input shaft are a one piece
assembly A3. The assembly is permanently driven by the
engine via the torque converter. Clutch counter plates 3 are
also permanenty driven via meshing teeth inside the clutch
housings.
Clutch friction plates 4 are meshed with the gear/plate
carriers (G1 and G2).
In the diagram, clutch A1 is engaged. The counter plates 3
and friction plates 4 are pressed together by hydraulically
actuated piston 5. Drive is then transmitted from the input
shaft to the gear G1.
Clutch A2 is disengaged and no drive is transmitted to
gear/plate carrier G2. The gear is also free to rotate on the
input shaft assembly.
Actuation of the hydraulic pistons 10 and 5 is controlled via
two position solenoid valves E1 and E2
†
.
When neutral is selected, solenoids E1 and E2 are
deactivated and the flow of pressurised oil to the clutches is
blocked. Springs 8 and 9 move the pistons away from the
clutch plates and oil from both pistons is vented to the
sump.
When for example clutch A1 is selected to be engaged,
solenoid valve E1 is energised and solenoid valve E2 is de-
energised. Pressurised oil is diverted via cross drillings
inside the input shaft A3 to the clutch piston 5. Pressure
from clutch A2 is vented to the sump via the solenoid valve
spool E2. Oil is prevented from leaking by seals 6 on the
pistons and ring seals 7 on the input shaft A3.
† The valve E is shown using symbols. For an explanation of
how the symbols work, see Section E, Introduction to
Hydraulic Schematic Symbols.
Clutch Operation - Mainshaft, Layshaft, 6 Speed
The mainshaft, layshaft and 6 speed units all incorporate
one clutch and not two, as in the forward and reverse units.
The operation of the single clutches is the same as for one
clutch in the forward or reverse units.
Clutch Operation - 2/4 Wheel Drive Clutch
The 2/4 wheel drive clutch is similar to the Synchro Shuttle
2/4 wheel drive clutch. See Synchro Shuttle Gearbox, 2/4
Wheel Drive Clutch Operation.
30 - 1 30 - 1
Systems Description
Section F Section F
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