Gamma Goat
Gamma Goat
Gamma Goat
Gamma Goat
Gamma Goat
Gamma Goat


VIN: 2252-4628C
ID Number: M561 "Gamma Goat"
Type: 6x6 Cargo
Designer: Chance-Vought Aircraft
Manufacturer: CONDEC
Gross Weight: 7,275 lbs
Length (Overall): 227 inches
Width (Overall): 84 inches
Height (Top Up) 91 inches
Crew: 1
Suspension: Wheel 6x6
Range: 285 miles
Operational Range:>/th> 420 miles
Max Speed: 56 MPH
Transfer Case: 2 Speed Dana 18
Wheelbase: 80 inches
Engine: Detroit Diesel 3-53
Engine Type: Diesel I3
Cubin Inch: 160 cu in (2.6 L)
Horsepower:/th> 101 hp (75 kW), 217 lbf⋅ft
Owner: Estrella Warbird Museum


Designed by Chance-Vought Aircraft and built from 1969 to 1973, the M561 is a six-wheel drive semi-amphibious off-road 1 ¼ ton cargo truck used by the U.S. military in the Vietnam War. The front and rear units are connected and articulated but do not bend around turns. The steering was unusual in that the front and rear wheels turned in opposite directions, making for wide turns. The body is aluminum to help reduce weight for “swimming,” but its amphibious characteristics were limited to calm water fording only. As for its appearance, beauty is in the eye of the beholder. This example was manufactured circa 1970 and has a USMC paint scheme and Detroit Diesel 3-53N 3 cylinder diesel engine. Over 1,700 Gama Goats were built for the USMC.

The vehicle's nickname came from two sources: "Gama" from the name of the inventor of its powered articulated joint, Roger Gamaunt, and "Goat" for its mountain goat-like off-road ability. Its military designation was M561, 6×6 tactical 1¼-ton truck. There was also an ambulance version known as the M792. The vehicle was replaced by a variety of Commercial Utility Cargo Vehicles (CUCV) and Humvees (HMMWV).

Pictured above is the vehicle as it was recently received. We are looking for Gamma Goaters out there who would be interested in helping us restore this Goat to its original condition. Or, if you are interested in donating to its restoration, click on the "Donate" button in the header.

Overall, some 14,274 Gama Goats were built at a cost of US$8,000 each (1965 dollars; equivalent to $68,790 in 2021); this was considered quite high at the time. 12,516 were slated for the US Army and 1,758 for the USMC. While the Gama Goat had exceptional off-road ability, its quirky steering made it hard to handle on pavement, and its tendency to flounder in amphibious operations required drivers to have special training in order to operate it. This meant that it could not be the "general purpose" vehicle the Army had hoped for, and production was halted after the original contract expired.

The air-cooled engine used in the original prototypes overheated in use, and was replaced in the production vehicles with a liquid-cooled Detroit 3-53 Diesel engine. Due to the high-intensity noise from the two-stroke Diesel engine, the drivers required hearing protection. The double hull construction and complex articulated drivetrain made maintenance difficult (the lubrication order alone took around six hours). In service in Vietnam, Gama Goats would often be sent out ahead of other vehicles in order to arrive at their destination at the same time.

While technically listed as amphibious, the Gama Goat's swimming capability was limited to smooth water crossings of ponds, canals and streams due to the very low freeboard and the lack of a propeller. Propulsion in the water was supplied by the six spinning wheels, and bilge pumps were standard equipment. Drivers had to remember to close the hull's drain openings before swimming the vehicles. Some models had extra equipment installed that made them too heavy to swim, such as heavy-duty winches, communications shelters that made them top heavy, or radar gear.

Tht M561 Gamma Goat was designed to be air-transportable and droppable by parachute.

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