M809 series trucks

M809 Series 5-ton 6x6 Truck
M813 crossing a river
Type	5-ton 6x6 trucks
Place of origin	United States
Production history
Manufacturer	AM General
Produced	1970–1982
Specifications (M813 with winch)
Weight	21,020 lb (9,530 kg) (empty)
Length	26 ft 7 in (8.10 m)
Width	8 ft 2 in (2.49 m)
Height	9 ft 9 in (2.97 m)
Engine	Cummins NH250 240 hp (180 kW)
Transmission	5 speed x 2 range
Suspension	Live beam axles on leaf springs
Operational range	350 mi (563.3 km)
Speed	52 mph (84 km/h)

The M809 Series 5-ton 6x6 truck (G908) was a family of heavy tactical trucks built for the United States Armed Forces. The basic cargo version was designed to transport a 5-ton (4,500 kg), 14 ft (4.3 m) long load over all terrain in all weather. In on-road service the load weight was doubled. Built by AM General, they evolved into the M939 Series.

In the late 1960s the US Army needed more 5-ton (4,536 kg) 6x6 trucks. AM General developed an updated version of the M39 series, in service since 1951. The primary difference was the engine and transmission. The hood and grille were lengthened to make room for the larger engine and the lighting system was updated to meet new US safety regulations. All had an air cleaner on the left fender, a way to tell them from the earlier M39 series.

AM General built all M809s between 1970 and 1982. The M809 Series was then improved into the M939 series in 1982. The first 11,000 M939s were rebuilds of M809s.

The M809 series used a Cummins NH250 engine, a 855 cu in (14.0 L) naturally aspirated inline 6 cylinder diesel engine developing 240 hp (180 kW) at 2100rpm and 685 lbf·ft (929 N·m) of torque at 1500rpm. All models of the M809 series used this engine throughout their service life. The N series was a successful commercial design, with a conservative rating the engine was more powerful and less stressed than the Continental LDS-465 multifuel engine used in the M39 series.

A Dana-Spicer 5-speed model 6453 synchromesh manual transmission had a very low 1st, direct 4th, and overdrive 5th. A Rockwell-Standard 2-speed transfer case also engaged the front axle automatically if the rear wheels turned faster than the front, as when the rear wheels spun.