The M561 Gama Goat was designed by ARPA-funded Project Agile, as a truck to partially replace the fleet of M37 vehicles, capable of handling the rugged terrain of Southeast Asia. The DOD’s program for the M561 cargo truck was initiated in May 1961. The truck was developed during the period March 1963 through June 1966, and in June 1968 the initial production contract was awarded. Ling-Temco-Vought (LTV) was the prime contractor with production by Consolidated Diesel Electric Company (CONDEC). Of the original production, in 1971-73 4,348 trucks were retrofitted at Army depots to correct deficiencies found during Initial Production Testing (IPT), including 1758 vehicles purchased by the Marine Corps. As of 31 December 1972, the contractor had built 12,353 vehicles and 12,081 were accepted by the Army. The final contract amount was $135.2 million for 14, 274 production trucks, includes the 1,758 for the Marine Corps. The M561 program was concluded in July 1973. Figures from GAO Staff Study, February 1973.

The M561 Gama Goat is powered by a Detroit Diesel 3-53 power plant mounted behind the driver’s cab in the two axle tractor. The trailer had its own powered single axle, a true 6×6 design. Both the front axle and the rear axle on the trailer were steered, giving the Gama Goat extraordinary capabilities to move in tight places. The aluminum body was watertight allowing the Gama Goat to cross waterways, but it had no propeller and could swamp easily which limited its amphibious ambitions.

The vehicle had many drawbacks, however, including mechanical problems, high noise and unusual handling requiring special driver training. Over 15,000 were produced before production ended. It was replaced by the HMMWV.