Towards the end of
World War II, tracked, fully enclosed armored personnel carriers were developed based on the
M18 Hellcat. These were first the M39 (T41) and then M44 (T16) carriers. Like the improvised 'Kangaroo' carriers of WWII the M39 kept the location of the rear engine and required its occupants to exit over the sides, but the M44 reworked the tank's body completely and moved the engine to the front, allowing more internal space and rear doors. The M44 was extremely large (51,000 lb combat weight), carrying 24 infantry as well as a driver, bow gunner and vehicle commander. It was evaluated at
Fort Knox and
Aberdeen Proving Ground after the end of the war, but, ultimately, the army rejected the M44 as being too large - at the time, their tactical doctrine required infantry squads of ten men. As a result, only a handful of M44s were built, seeing service in a number of auxiliary roles. On 21 September 1945, a set of requirements were laid down for a squad sized armored personnel carrier, based on the chassis of the T43 cargo carrier. On 26 September 1946, the development of the T18 armored utility vehicle, based on the running gear of the
T41 light tank, was approved with
International Harvester (IHC) contracted to produce four prototypes. The original mockup, which was designed to carry 14 people, including crew, featured two remote controlled .50 caliber machine guns, which could be aimed remotely by either the commander or either of the two gunners. The first prototype in 1948
T18 dropped the assistant driver, but retained the remote controlled machine guns. The
T18E1 pilot was unarmed and had a high cupola for the commander, this is sometimes referred to as pilot number 4. The
T18E2 replaced the commander's cupola with a T122 machine gun mount, which could be fitted with either a .30 or .50 caliber machine gun. Though the original T18E1 prototype was unarmed, the high cupola was replaced with a variety of machine gun mounts before the M13 cupola, with a .50 caliber machine gun, was evaluated. The prototypes were originally powered by a six-cylinder Continental AO-895-2 air-cooled gasoline engine, which exhausted through the hull side grills. This was later replaced with the AO-895-4 in the T18E1, which exhausted through a pipe mounted horizontally across the front of the vehicle. After acceptance testing, the T18E1 was ordered into production in 1952 as the M75. An order for 1,000 was placed with IHC and another, for 730, with the
Food Machinery and Chemical Corporation. Numerous changes were made during the production run to reduce the cost and complexity. The number of shock absorbers was halved from four per side to two, and an auxiliary generator/heater was deleted. The two 75 gallon rubber fuel tanks were replaced by a single 150 gallon metal one. The M75 shared many chassis/suspension components with the
M41 Walker Bulldog light tank, which was also powered by a Continental air-cooled engine. It had a
cross-drive transmission (permitting pivoting, etc.), but was steered through two vertical handles, simulating the laterals of earlier vehicles controlled by track clutching/braking. The approximate cost of the vehicle was $72,000, which contributed to the early halting of production. The high profile (height) of the vehicle was also a negative factor. Additionally, the engine air cooling vents were considered to be vulnerable to
small arms fire. However, the reliability of its drive system was far superior to that of its replacement, the
M59. ==Description==