TM-9-2320-272-23-1
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5
SEPTEMBER 2012
TM-9-2320-272-23-1 - Page 182 of 1313
FIELD MAINTENANCE
EQUIPMENT DESCRIPTION AND DATA
EQUIPMENT CHARACTERISTICS, CAPABILITIES, AND FEATURES
The M939, M939A1, and M939A2 (M939/A1/A2) series of vehicles are varied in design and capabilities. The M939
was a redesign and retrofit of the M809 series of vehicles, providing enhanced capabilities.
The leading features of the M939 are:
•
Automatic transmission (Allison MT654)
•
Hydraulic-assisted power steering system
•
Complete airbrake system
•
Improved cooling system
•
Three-crewmember cab
•
Tilt hood
Changes were incorporated into later production engines (after engine serial number 11246663) which provided for
control of exhaust gas recirculation back to the air intake manifold and the use of top-stop injectors to make up a
clean air configuration.
The M939A1 improved on the M939 by adding 14:00xR20 super-sized tires, increasing the minimum road clearance
and approach and departure angle. This necessitated a modification to the spare tire rack and lifting device used on
all series vehicles.
The M939A2 incorporated a new engine (Cummins 6CTA8.3) and the Central Tire Inflation System (CTIS).
The M939/A1/A2 series vehicles can be distinguished from the M809 series by the following features:
On the left side, the exhaust was moved behind the cab and tilted out so exhaust gases clear the side of the vehicle.
Hood latches were installed on the sides of the hood near the mirrors. The battery box was incorporated into the
companion seat to improve battery life in cold climates. A steering-assist cylinder was installed between the right
front frame rail and the right axle hub.
From the front, the hood and fenders are an assembly which tilt forward for access to the engine compartment. A
tilt handle and locking device was installed to tilt and hold the hood in a secured open position.
The air filter was moved under the driver's door and the intake stack was brought up behind the cab, even with the
cab top.
Cargo Trucks With Dropsides: M923/A1/A2 WO/W and M925/A1/A2 W/W. These vehicles are used to transport
cargo and troops. The vehicles have a payload rating of 10,000 lbs (4,540 kg) and provide 550 cu-ft (15.4 cuM) of
cargo space. Removable dropsides and tailgate permit hauling of extra wide loads and easy access for unloading
cargo. Troop seats, bows, and canvas are also available. The M925/A1/A2 models have front winches and can be
used for recovery operation. The bed of the M923A1/A2 and M925A1/A2 has been shifted back to facilitate a new
lifting davit and spare tire mount. When the tire is mounted in its storage location on the M923A1/A2 and
M925A1/A2, the top of the tire extends above the minimal reducible height and may need to be removed to obtain
the necessary measurement.
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