TM-9-2320-272-10
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; OPERATOR'S MANUAL
SEPTEMBER 2004
CHANGE 2
TM-9-2320-272-10 - Page 264 of 481
TM 9-2320-272-10
Change 2
2-156.7
WARNING
• When the ABS senses impending wheel lockup, the ECU will
modulate the relays which will repeat a “release and
recharge” cycle of air in the brake chambers. Unlike a car’s
ABS, where you can feel this modulation on the brake pedal,
you will not feel any modulation of the brake pedal on an air
brake system. When the ABS does modulate, you will feel a
jerking sensation of the vehicle as the brakes rapidly release
and lock. Failure to comply may result in damage to vehicle
or injury or death to personnel.
• M939 series vehicles have a conventional air brake system,
which is very sensitive. Drivers of these vehicles must be
well-trained in operating tactical vehicles with air brakes.
Air brakes are unique because braking force is proportional
to pedal travel, but the driver does not experience resistance
from the brake pedal. An inexperienced driver may respond
to lack of resistance by applying too much force to brake
pedal. Operators can be confident that M939 series trucks
equipped w/ABS brakes have more than adequate brake
capacity for safe mountain terrain operations.
• Do not drive too fast for total weight of vehicle, amount of
fuel in tanker, length and angle of grade, road conditions,
and weather. Failure to do so may result in damage to
vehicle or injury or death to personnel.
• Comply with warning signs indicating length and angle of
grade. Failure to comply may result in damage to equipment
or injury or death to personnel.
• Ensure vehicle is moving 10–15 mph (16–24 km/h) slower
than posted ramp speed for entrance or exit ramps. Failure
to comply may result in vehicle rollover, causing damage to
vehicle or injury or death to personnel.
d. Convoy Integrity.
For convoys that include medium tractors transporting
petroleum tankers, convoy speeds will be established in advance of movement so as
not to exceed the maximum safe speed of the slowest transport equipment operating
within each convoy. Convoy briefings will set forth the speed restrictions with a
clear statement to all convoy participants as to the purpose and reasons for such
speed restrictions.
2-26.2. OPERATION OF M931/A1/A2 W/ABS AND M932/A1/A2
W/ABS TRACTORS WHEN TOWING M131 SERIES,
M967/A1, M969/A1/A2, AND M970/A1 5,000-GALLON
FUEL TANKERS
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