LR3/Disco 3
The transfer box is designed to allow range changes when the vehicle is moving, providing the transmission speed
complies with the preset thresholds determined by the transfer box control module. For additional information, refer to
Four-Wheel Drive Systems
(308-07A Four-Wheel Drive Systems)
The transmission speed sensor is a Hall effect sensor and is located at the rear of the transmission. The sensor measures
the speed of the transmission output shaft from a single tooth reluctor on the output shaft.
Hall effect sensors require a supply current, which allows the sensor to detect zero movement. Hall sensors use the
principle of a voltage, which is generated across a semiconductor carrying an electric current. The voltage is generated
when the transmission output shaft reluctor is exposed to magnetic flux.
When the semiconductor is exposed to a magnetic flux, the electron flow through the semiconductor is deflected creating
a potential difference across the semiconductor. This difference in voltage is called the Hall effect. It is this voltage that
the transfer box control module uses to establish the speed of the transmission output shaft.
When the reluctor is near the sensor, the sensor produces a low voltage output. When the reluctor is away from the
sensor, the sensor produces a high output voltage (battery voltage).
The sensor connector has three wires; one is used for sensor earth, one is supply current, from the transfer box control
module, and the other is the signal output to the transfer box control module.
SERVICE
The ZF S6-53 manual transmission is a black box unit. Therefore the repairs permitted are limited to:
Oil drain plug
Oil filler plug
Layshaft sealing cap
Input shaft seal
Gear position sensor and magnet assembly
Selector shaft seal
Speed sensor
Output shaft and output shaft seal.
Item Part Number Description
1
-
Speed sensor
