M939 Truck

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M939 series
A United States Marine Corps M923
Overview
Manufacturer AM General[1]
BMY (After 1986 & M939A2)[1]
Production 1982[1]
1989 (M939A2)[1]
Body and chassis
Body style 2-door General Utility Truck[1]
Layout 6x6
Powertrain
Engine Cummins NHC-250 (M939/M939A1)
Cummins 6CTA8.3 (M939A2)
240 hp (180 kW)
Transmission Allison 5 speed automatic
2-speed transfer case
Dimensions
Length 307.4 in (781 cm)
Width 97.5 in (248 cm)
Height 115 in (292 cm)
Curb weight 21,470 lb (9,740 kg)


The M939 series 5-ton 6x6 truck is a family of United States military logistical transportation trucks which was designed in the late 1970s and has been in service ever since.[1] About 32,000 M939 series trucks are in service.[1] The M939 series is an improved version of the older M809 Truck series of trucks.[1]

Specifications[edit]

U.S. Marine Corps M923
M929 Dump Truck with armored cab

All models of the M939 share a common basic chassis, cab, and hood/fenders. The basic truck is a 6x6 (three axles, six sets of tires, all six powered) medium truck. Early M939s were rebuilds of M809 vehicle chassis by AM General, with a new automatic transmission, cab, and hood/fender. Suffix –A2 are new production by Bowen-McLaughlin-York/BMY with later model Cummins engine. The vehicles have a wide variety of configurations and weights. [2][3][4]

Note that the motor and tire specifications, along with other improvements, apply to the A2 versions (and A1 versions) of each base model listed below. There is an M928, an M928A1, and M928A2.

Engine[edit]

The M939 and M939A1 models use a Cummins NHC 250 855 cu in (14.0 L) naturally aspirated diesel engine, producing 240 hp (180 kW) at 2100rpm and 685 lbf·ft (929 N·m) at 1500rpm. This was the standard engine of the M809 series. The M939A2 models use a newer and smaller Cummins 6CTA8.3 504 cu in (8.3 L) turbocharged diesel engine producing 240 hp (180 kW) at 2100 and 745 lbf·ft (1,010 N·m) at 1500rpm. All models have an Allison 5 speed automatic transmission with a two speed transfer case. [5][6]

Tires[edit]

The M939 uses 11:00 R20 tires with two tires per side per axle in the rear (rear tandem duals). The M939A1 and M939A2 series use oversized 14:00 R20 tires and rear tandem singles. M939A2 series vehicles use a centralized tire inflation system (CTIS).

Models[edit]

The M939 series includes the following models:[7]

Model Description Chassis
M923 Cargo with 14 ft (4.3 m) dropside bed 179 in (454 cm) wheelbase
M924 Cargo 179 in (454 cm) wheelbase
M925 Cargo with dropsides and winch 179 in (454 cm) wheelbase
M926 Cargo with winch 179 in (454 cm) wheelbase
M927 Cargo with 20 ft (6.1 m) bed 215 in (546 cm) Extra Long Wheelbase (XLWB)
M928 Cargo with winch 215 in (546 cm) Extra Long Wheelbase (XLWB)
M929 Dump 167 in (424 cm) Short wheelbase
M930 Dump with winch 167 in (424 cm) Short wheelbase
M931 Semi-tractor 167 in (424 cm) Short wheelbase
M932 Semi-tractor with winch 167 in (424 cm) Short wheelbase
M934 Expansible van body 215 in (546 cm) Extra Long Wheelbase (XLWB)
M935 Expansible van body with hydraulic lift gate 215 in (546 cm) Extra Long Wheelbase (XLWB)
M936 Wrecker with winch 179 in (454 cm) wheelbase

Operators[edit]

Safety[edit]

The safety of the M939 series of trucks has been criticized, especially braking performance and stability when loaded. In 1999 the U.S. Army began refitting anti-lock brake systems to the M939 trucks. Until the trucks were modified, they were limited to a 40 mph (65 km/h) top speed by an Army-wide safety order.

Prior to that improvement, 26% of all Army vehicle accidents and 53% of all Army vehicle accident fatalities were in M939 series trucks. From 1987 to 1998 the series made up 9% of the total U.S. Army vehicle inventory, but accounted for 34% of all fatal accidents. [8]

The problem seemed to be that the torque converter would "lock up" in 2nd gear, and would not unlock easily. When the driver attempted to brake hard, often in a sudden or 'panic' stop, and accidentally locked the brakes (no wheel movement, tires skidding), this would kill the engine; this also killed the power steering, and the driver would suddenly be unable to steer. Too often, the truck would veer sideways and either hit something or roll over.

See also[edit]

References[edit]

  1. ^ a b c d e f g h "M939, General utility truck". military-today. Retrieved 2013-10-12. 
  2. ^ TECHNICAL MANUAL OPERATOR’S MANUAL FOR TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL), U.S. Army TM 9-2320-272-10, Accessed 2006-05-04
  3. ^ Crismon, Fred W. (1998). Modern U.S. Military Vehicles. MBI Publishing. pp. 91–96. ISBN 0-7603-0526-9. 
  4. ^ Doyle, David (2003). Standard catalog of U.S. Military Vehicles. Kraus Publications. pp. 202–203, 205. ISBN 0-87349-508-X. 
  5. ^ Crismon (1998), p. 95.
  6. ^ Doyle (2003), p. 203-204.
  7. ^ Doyle (2003), p. 200-204.
  8. ^ M939 series information page at globalsecurity.org, Accessed 2006-05-04

External links[edit]