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M-123 Truck, Tractor, 10-Ton, 6x6

The M-123 Truck, Tractor, 10-Ton, 6x6 is part of the G-792 series of vehicles which includes the M-125 Truck, Cargo, 10-ton, 6x6. The M123 is a tractor for hauling semi-trailer loads such as heavy vehicles (tanks, bulldozers) or ammunition or other supplies. Its gearing restricts it use to off-road field activity, not line haul.

This huge tractor was manufactured by Mack from 1955 to 1957 (the M123 series) and 1965 to 1969 (M123A1C), the successor to the M26 'Dragon Wagon' tractor. One or two winches, depending on the variant, were mounted behind the cab, used to draw loads onto a trailer or a trailer onto the fifth wheel. Variant differences included the engine, fifth wheel height, and details like a warning beacon, clearance and turn signal lights, and access steps. Tires were 14.00x24 inch.

M-123A1C Truck, Tractor, 10-Ton, 6x6.  Photo courtest of Oshkosh Equipment Sales, LLC
M-123A1C Truck, Tractor, 10-Ton, 6x6. Photo courtesy Oshkosh Equipment Sales, LLC.

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M-123 Truck, Tractor, 10-Ton, 6x6 (G-792)

The M-123 Truck, Tractor, 10-Ton, 6x6 was produced in model variants that included:

  • M123 FSN 2320-395-1875. Dual rear winches. LeRoi T-H844 V8 Gas engine.
  • M123E2 FSN 2320-879-6177. Dual rear winches, Cummins V8-300 diesel.
  • M123C FSN 2320-294-9552. Single rear winch. Cummins V8-300 diesel.
  • M123D FSN 2320-542-2509. Dual rear winches. Cummins V8-300 diesel.
  • M123A1C FSN 2320-226-6081. Single rear winch, 36,000lb lift crane. Cummins V8-300 diesel.

The C variants had a single rear winch and low mounted fifth wheel. The M123D was the same as the M123C, but with dual rear winches. Later M123 variants were assembled by Consolidated Diesel Electric Company (CONDEC) from Mack components. After total production of approximately 4,000 vehicles, the M123 10-ton tractor was superseded by the heavier and more powerful Oshkosh M911 C-HET tractor.

The M123 series trucks were mated with the M15A2 50-ton semitrailer which was later superseded by the M172A2, M747 and other semitrailers.

Find additional photos and hi-res versions of the M-123 Truck, Tractor, 10-Ton, 6x6 at the Olive-Drab Military Mashup:

M123 10T tractor.
M123A1C Truck, Tractor, 10-Ton, 6x6 vehicles in convoy, each with a trailer carrying a Rome Plow bulldozer, Long Binh, Vietnam, 21 April 1970.  984th Land Clearing Company, 62nd Engineer Battalion.
M123A1C Truck, Tractor, 10-Ton, 6x6 participates in debris removal during recovery operations following Hurricane Camille, Mississippi coast area, circa 17 August 1969.
M123A1C Truck, Tractor, 10-Ton, 6x6 Courtesy: Oshkosh Equipment Sales Corporation
1968 Mack M123A1C Truck, Tractor, 10-Ton, 6x6.  For sale by private party, August 2011. Courtesy: Mylittlesalesman.com
M123A1C Truck, Tractor, 10-ton, 6x6 (Mack Truck) Courtesy Oshkosh Equipment Sales

M-123 Truck, Tractor, 10-Ton, 6x6 Characteristics

Engine: M123
Engine: M123A1C and others
LeRoi T-H844 V8 Gas 297hp@2600rpm
Cummins P1525 V8-300 785 cu in, diesel 300hp@3000rpm
TransmissionConstant mesh Mack TRD XT72 5 fwd, 1 rev
Transfer caseMack constant mesh 2 speed (integrated w/transmission)
Front AxleMack triple reduction
Rear AxlesMack double reduction
DifferentialsMack 10:1
WinchGarwood 45,000 lbs
Fuel capacity2 tanks, 83 gal each
Cruising range300-350 miles
Maximum speed43 mph
Weight: M123
Weight: M123A1C
32,250 lbs
29,100 lbs
Length289 inches (7.34 m)
Width114 inches
Height: M123
Height: M123A1C
113 inches
108 inches
Towed load rating120,000 lbs highway / 80,000 lbs off highway

For transport, the overall height can be reduced to 93.0 inches (2.36 m) by lowering the windshield and by removing the floodlight, spare wheel, spare wheel davit, trolley tracks, level wind trolleys, hydraulic control handle, and operator's cab cover.

To assist with operations during conditions of limited visibility, the M123 is equipped with a swivel-mounted floodlight on a stanchion at the left rear of the cab.

M-123 Truck, Tractor, 10-Ton, 6x6 Manuals and Documentation

Some of the manuals for the M-123 Truck, Tractor, 10-Ton, 6x6 are:

  • ORD 7 SNL G792 (31 January 1958) Section I, LeRoi engine parts.
  • TM 9-8002 (1 November 1955)
  • TM 9-8003-1 (25 June 1956) Ordnance Maintenance for Engine, Engine Accessories and Clutch
  • TM 9-2815-213-34 Cummins V8-300 Maintenance
  • TM 9-2320-206-10 (29 April 1977) Operator's Manual
  • TM 9-2320-206-10 (8 December 1978) HR Hand Receipt
  • TM 9-2320-206-12 (4 February 1960) Supersedes TM 9-8002 & ORD 7 SNL G792
  • TM 9-2320-206-20 (22 October 1971) Organizational Maintenance
  • TM 9-2320-206-20P Parts
  • TM 9-2320-206-34 Direct & General Support Maintenance
  • TM 9-2320-206-34P (6 March 1972) Direct & General Support Maintenance Repair Parts & Special Tools List
  • TM 9-2320-206-ESC
  • LO 9-2320-206-12 Lube Order

Thanks to Corjan de Wit of Middelburg, the Netherlands, you will find TM 9-2320-206-12 (M123 and M125) at the linked page.

This Olive-Drab.com page describes the manual numbering system.

The M-123 Truck, Tractor, 10-Ton, 6x6 is extensively described on the linked page from the VanNatta Truck Museum with many photos and detailed technical discussion.

M-123 Truck, Tractor, 10-Ton, 6x6 Photo Gallery

M-123A1C
M-123A1C Truck, Tractor, 6x6, 10 Ton.

M-123A1C
M-123A1C Truck, Tractor, 6x6, 10 Ton.

An M-123A1C Truck, Tractor, 10-Ton, 6x6 with an M747 semi-trailer loaded with an M-110 8in (203mm) Self-propelled Howitzer August 1985
An M-123A1C Truck, Tractor, 10-Ton, 6x6 with an M747 semi-trailer loaded with an M-110 8in (203mm) Self-propelled Howitzer, August 1985.

M-123A1C Truck, Tractor, 10-Ton, 6x6.  Photo courtest of Oshkosh Equipment Sales, LLC
M-123A1C Truck, Tractor, 10-Ton, 6x6. Photo courtesy Oshkosh Equipment Sales, LLC.

Thanks to MSG J. Durham for help with this page.

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