Mack NJU 5-ton 4x4 truck

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Truck Tractor, Ponton, C. O. E., 5-6 ton, 4x4
(Mack Model NJU-1)
Mack NJU-12.tif
Mack NJU-1 Ponton tractor
Type5- to 6-ton 4x4 semi-tractor
Place of originUnited States
Production history
ManufacturerMack Trucks
No. built692 (+8 NJU-2)
Specifications (NJU-1[1])
Mass16,580 lb (7,520 kg)
Length19 ft 9 in (6.02 m)
Width8 ft (2.44 m)
Height9 ft 6 in (2.90 m)

EngineMack EN532
136 hp (101 kW)
Transmission5 speed x 2 range trf case
SuspensionLive axles on leaf springs

The Mack NJU 5- to 6-ton 4x4 Ponton tractor (G639) was a semi-tractor designed to haul bridging equipment during World War II. Of the 700 built 119 were supplied to the British in Egypt, 8 were built with van bodies, and the rest were used as a substitute standard by the US Army.


In 1940 the US Army ordered 700 Mack 4 x 4 truck tractors, intended to tow pontoon-carrying semi-trailers. 694 were delivered in 1941 and the last 6 in 1942. An Autocar design was standardized by the US Army and only 700 NJUs were built.

692 NJU-1 tractors and 8 NJU-2 vans designed to tow topographical trailers were delivered.

In November 1941 119 semi-tractors were delivered to the British army in Egypt, where they bore War Department H-numbers.

Some NJU-1's went into French Army service post war.[2]


Mack NJU-1

The design was a militarized version of a civilian Cab Over Engine (COE) model, partly redesigned to make it 4WD. A Mack engine and transmission were matched with a Timken 2-speed transfer case and double-reduction axles. The EN532 engine was a 532 cu in (8.7 L) L-head inline 6 cylinder gasoline engine developing 136 hp (101 kW) at 2500 rpm. The 5-speed transmission drove the separate transfer case.[3]

A ladder frame had two live beam axles on leaf springs with a 155 inches (3.94 m) wheelbase. There was a 15,000 pounds (6,800 kg) winch behind the front bumper and a pintle hitch at the rear. A civilian type closed cab was used, right behind the cab was an open cargo box used to carry engineer tools, outboard motors, and other equipment.

Early semi-tractors and all vans used 9.75x20 tires, later semi-tractors had 12.00x20 tires. All trucks had dual rear tires. All trucks had full-air brakes.[4]



  1. ^ Doyle, David (2011). Standard Catalog of U.S. Military Vehicles (2nd Edition). Krause Publications. p. 174. ISBN 0-87349-508-X.
  2. ^ Vanderveen, Bart (1998). A record of military Macks in the Services and beyond. After the Battle. pp. 41–42. ISBN 1-870067-09-6.
  3. ^ Crismon, Fred W (2001). US Military Wheeled Vehicles (3 ed.). Victory WWII Pub. p. 285. ISBN 0-970056-71-0.
  4. ^ Vanderveen (1998).

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