67 - 1
Section F
9803/3280
Section F
67 - 1
Issue 1
Service Procedures
Powershift Gearbox
Speed Sensor
Powershift machines fitted with an electronic control unit
(ShiftMaster ECU) or a speedometer have a speed sensor
D
fitted. The speed sensor detects the speed of rotation of the
gearbox output shaft and relays this information to the ECU
or speedometer as applicable.
The sensor detects the passing of the gear teeth on the
output gear. When adjacent to the top of a gear tooth the
sensor electrical output turns ON, when adjacent to a gap
between the teeth the sensor output turns OFF. In this way
the frequency of the electrical signal changes according to
the speed of gear rotation and therefore machine road
speed.
The ShiftMaster ECU uses the input from the speed sensor
to determine gear shift points. Failure of the speed sensor
or its wiring will enable an ECU ‘Limp Mode’, preventing the
use of 4th, 5th, and 6th gears. See
Fault Finding -
Powershift Gearbox
.
Testing
The speed sensor can be tested in situ without removing it
by means of service test harness 892/01096 .
1
Park the machine on firm level ground, engage the
parking brake and set the transmission to neutral.
Lower the loader arms to the ground. Switch OFF the
engine and remove the starter key.
2
Connect the test harness
E
as shown. Tie back and
secure the wires clear of the driveshaft and other
moving components, in a position where the light
emitting diode (LED) can be seen while operating the
machine.
3
Turn the engine ON and drive the machine forward
approximately 2 m (6 ft), make sure it is clear in front.
Alternatively raise the wheels off the ground. If the
sensor is operating correctly the LED will illuminate as
the gear teeth pass the sensor, when the speed
increases the LED will flash at a greater frequency until
becoming continuously illuminated at higher speeds.
4
If the LED fails to illuminate carefully check the relevant
wires and connectors for damage. Repair as required
and re-test the sensor as described above. It should be
noted that the speed sensor is normally a reliable
component and a fault is more likely attributed to
damaged wires or electrical connectors, see
Electrical
Connections - Powershift Gearbox - 6 Speed
.
A405380
A
B
C
E
D
Key:
A
Ground
B
+V
C
Output