Drive Axles, Detroit™ and Meritor™
For additional information regarding Meritor axles, visit the Meritor website at .
Drive Axles With Differential Lock
The optional driver-controlled differential lock should only be used under adverse road conditions where greater traction is needed. With the differential lock on, the turning radius is increased and vehicle handling is affected. The red differential lock indicator light illuminates on the dash message center when the differential lock is engaged.
A differential lock provides maximum traction under slippery conditions. When the differential lock is engaged, the clutch collar completely locks the differential case, gearing, and axle shafts together, maximizing the traction of both wheels and protecting against spinout. Do not exceed 25 mph (40 km/h) when the differential lock is engaged.
Under normal traction conditions, do not use the differential lock feature.
Differential Lock Switch
Notice: The differential lock should only be engaged when the vehicle is stopped or moving slowly at low throttle. This will prevent internal axle damage.
A two-position guarded rocker switch controls the differential lock. See Fig.. To lock the wheels together, momentarily press the upper half of the switch. To unlock the wheels, press the upper half of the switch again.
Fig. 1, Differential Lock Switch, Optional
Important: The differential lock rocker switch is guarded to prevent unintentional switch activation. If the light emitting diode (LED) in the switch begins to blink during normal operation, when the switch has not been activated, an error condition exists. Bring the vehicle to an authorized Freightliner service facility as soon as possible.
When the differential lock switch is pressed, three responses are possible: a normal response, a slow response, and an abnormal response.
Normal Response: The LED in the switch blinks until the axle has responded to the request to lock the wheels. At this point, the LED remains illuminated constantly. In normal operation, the wheels may lock so quickly that the blinking of the switch is barely noticeable.
If operation of the switch is not possible for any reason (ignition is turned off, vehicle is moving faster than 25 mph, etc.), the LED will stop blinking and turn off.
Slow Response: If operation of the switch is slowed for any reason (vehicle moving too fast, low air pressure, etc.), the switch will continue to blink until the wheels are able to lock. As in the normal response, the LED remains illuminated when the differential lock is engaged.
Note: If the vehicle is moving too fast, let up slightly on the accelerator. As the vehicle slows, the wheels will lock.
Abnormal Response: If the LED blinks for more than 30 seconds, the lock mechanism may not be fully engaged/disengaged. Bring the vehicle to an authorized Freightliner service facility for testing.
Differential Lock Operation
Warning: Locking the wheels when the vehicle is traveling down steep grades or when the wheels are slipping could damage the differential and/or lead to loss of vehicle control, causing personal injury and property damage.
Notice: The differential lock should be engaged when the vehicle is stopped or moving at a low, constant speed and the wheels are not spinning, slipping, or losing traction. Engagement at high speed or power can damage the axle(s).
Do not permit rear wheels to spin freely for more than ten seconds when traction is lost. Shift into lock to prevent damage to interaxle and main differentials.
Lock the wheels only when the vehicle is standing still or moving at very low speed, less than 5 mph (8 km/h). Never lock the wheels when the vehicle is traveling down steep grades or when the wheels are slipping.
Note: On some vehicles, the differential lock system is connected through the low speed range of the transmission. If this system is used, the transmission must be in the low speed range for the wheels to fully lock.
Warning: A vehicle with locked wheels can still slip sideways, causing possible loss of vehicle control, personal injury, and property damage.
Be especially careful when driving under slippery conditions with the wheels locked. Though forward traction is improved, the vehicle can still slip sideways.
If the vehicle is moving, maintain a constant vehicle speed when the differential lock is turned on. Briefly let up on the accelerator to relieve torque on the gearing, allowing the wheels to lock completely. When the wheels are fully locked, the turning radius will increase because the vehicle understeers. See Fig.. Drive cautiously and do not exceed 25 mph (40 km/h).
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Turning Radius When the Differential Lock is Engaged (understeer condition)
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Turning Radius When the Differential Lock is Disengaged
Fig. 2, Turning Radii
To disengage the differential lock after leaving poor road conditions, press the upper half of the switch, while maintaining vehicle speed. Let up momentarily on the accelerator to allow the wheels to fully unlock, then resume driving at normal speed.
Note: If the differential lock system is connected with the transmission in its low speed range, shifting out of the low speed range will also disengage the differential lock function. The switch will blink until the wheels unlock, and then go out.