Transmission
9803/7130 Issue 1
Syncro Shuttle Gearbox
This Illustration shows a typical JCB Syncro Shuttle
which consists of a torque converter, hydraulic
forward/reverse unit, and integral manual 4-speed
synchromesh gearbox.
The 4 gears are selected manually via a lever in the
cab. Drive is transmitted in forward or reverse
direction (in any gear) by means of the
forward/reverse unit A. When reverse is selected,
drive is transmitted via an idler gear which has the
effect of reversing the gear train.
The forward/reverse unit A has a pair of
hydraulically operated clutches giving forward -
neutral - reverse drive. Oil pressure is provided by a
crescent type pump B driven at engine speed by
the drive lugs of the torque converter C. The oil
pressure is controlled by maintaining valve D, and
clutch selection is achieved by means of an electric
solenoid valve E.
Drive is transferred from the forward/reverse unit by
helical gears to the mainshaft F, which carries the
3rd/4th synchromesh unit G, and to the layshaft H,
which carries the 1st/2nd synchromesh unit J. The
synchromesh units are of the 'Blocking Pin' type,
for a full detailed description refer to Synchromesh
- Description of Operation.
Drive is transmitted finally via the output shaft K to
the front and rear axles. The output shaft also
incorporates a brake disc/calliper type parking
brake L.
The illustration shows a gearbox which also
incorporates a P.T.O. M, for a full detailed
description refer to Power Take Off Clutch -
Operation.
Note: The P.T.O. is not fitted on some machine
variants.
Component Identification
Key
A Forward/Reverse Clutch Unit
B Oil Pump
C Torque Converter
D Pressure Maintaining Valve
E Solenoid Valve
F Mainshaft
G 3rd/4th Synchromesh Unit
H Layshaft
J 1st/2nd Synchromesh Unit
K Output Shaft
L Brake Disc
M Power Take Off
N Oil Filter
P Pressure Relief Valve
Associated Components
S Oil Cooler (gearbox oil)
S1 Oil Temperature Sender
T Forward/Reverse/Neutral Control Lever
(electrical)
U Gear Lever
V Transmission Dump Switch (electrical)
W Electrical Relays (solenoid valve)
3 - 2
3 - 2
Basic Operation
Section F Section F
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