freightliner M2 Plus 2023 Manual page 198

Drive Axles
When the interaxle lock is not engaged, there is
differential action between the two axles. The
differential compensates for different wheel speeds
and variations in tire size. Keep the interaxle lock
disengaged when driving on roads where traction is
good.
When the interaxle lock is engaged, the differential
action between the two axles is locked. Both drive
axles now share the power. Both axles, and both
sets of wheels, turn together at the same speed. The
interaxle lock should be used when the vehicle
encounters poor traction conditions; however, it also
increases drivetrain and tire wear and should be
used only when improved traction is required.
Interaxle Lock Switch
A two-position guarded rocker switch, shown in
Fig. 16.3, controls interaxle lock, causing both axle
shafts to rotate together. To lock the axles together,
press the upper half of the rocker momentarily (at the
red LED). To turn off interaxle lock, press the lower
half of the rocker (at the double-axle icon).
IMPORTANT: The interaxle lock rocker switch is
guarded to prevent unintentional switch
activation. This switch does not have a
diagnostic blink function when inactive.
When the interaxle 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 interaxle lock is engaged. At this point, the LED
comes on steady and stays illuminated. In normal
operation, the interaxle 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 too
fast, etc.), the LED will stop blinking and turn off.
Slow Response: If operation of the switch is slowed
for any reason (by cold weather, low air pressure,
etc.), the switch will continue to blink until the axles
lock together, or for a maximum of 10 seconds. As in
the normal response, the LED comes on steady and
stays illuminated.
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.
16.3
Interaxle Lock Operation
To engage interaxle lock and achieve maximum
pulling power in slippery or hazardous road
conditions, operate the interaxle lock switch as
discussed above, while maintaining vehicle speed.
Let up momentarily on the accelerator until the axle
lock engages. Proceed over poor road conditions
with caution. Do not wait until traction is lost and the
tires are spinning before engaging the interaxle lock.
NOTICE
Do not turn on the interaxle lock switch when the
tires are slipping. Do not continuously operate
the vehicle with the interaxle lock engaged
during good road conditions. To do so could
result in damage to the axle gearing and
excessive tire wear.
To disengage the interaxle lock after leaving poor
road conditions, operate the interaxle lock switch as
discussed above while maintaining vehicle speed.
Let up momentarily on the accelerator to allow the
axles to fully unlock, then resume driving at normal
speed.
Axle Shift
NOTICE
To prevent transmission and axle damage, make
sure the automatic transmission is in high range
when performing an axle shift with the vehicle
moving.
Axle shift is a function installed on vehicles with two-
speed axles to allow the use of the low speed range
when greater traction and maximum pulling power is
needed at low engine speed (rpm).
Under normal operating conditions, the vehicle is
operated using the high-speed gear ratios of the
axle. Under extreme weather or off-road conditions,
at low speed and rpm and/or to pull heavy loads, the
vehicle must be operated using the low-speed, or
reduction, gear ratios of the axle.
Axle Shift Switch
The axle shift switch is a two-position guarded rocker
switch installed on vehicles with two-speed axles.
See Fig. 16.4.
To shift the axle from low speed to high speed, press
the upper half of the rocker momentarily (at the