The M4 was based on the chassis and drive train of the obsolescent M3 Light Tank which introduced the trailing idler. One variant was designed to tow the 90 mm anti-aircraft gun, and another was for the 155 mm gun or 8-inch howitzer. The rear compartment carried the gun crew and other equipment and some later variants included a crane to assist with heavier projectiles. Two types of ammunition boxes were used on all models: a 90 mm box with side "tailgates" to access 90 mm shells pigeon-holed in the sides, and a combination box for 155 mm or 8-inch ammunition.
History
The M4 was built by tractors manufacturer Allis-Chalmers of West Allis, Wisconsin, starting in 1943 and was in U.S. military service until approximately 1960. After WWII, under the US Mutual Defense Assistance Program, M4s was supplied to Greece, the Netherlands, Japan, Brazil, Yugoslavia and Pakistan and several other states friendly to the USA. In the Indo-Pakistani War of 1965 the Pakistani Army used M4 Tractors to haul their M115 Howitzers to the battlefield of Chamb and then to the front at Lahore during the fighting with Indian troops.
Variants
M4: base model. 2,464 were configured to tow the 90 mm antiaircraft gun, while 3,088 were configured to tow the 155 mm gun or 8-inch howitzer
M4C: The "C" designation indicates spare ammunition racks configured in the crew compartment.
M4A1: The "A1" modification designates the wider suspension used for the "duck bill" tracks mirroring the E9 modification on Sherman tanks. 259 were built in 1945, and were used post-war as a prime mover for the M23 ammunition trailer in M40 Gun Motor Carriage sections.
Civilian use
After the war many types of these tractors were stripped of their military components and used for log skidders and power line construction. Many were used as carriers for rock drills, used in logging road construction in British Columbia. The first prototype was designed in the early 1960s by G.M. Philpott Ltd. of Vancouver, BC, and Scott-Douglas Industries, who supplied the M4 Carrier. It was used by MacMillan, Bloedel, and Powell River Company at their Juskatla, BC logging operation. Many improvements were made and when Finning Tractor later bought G.M. Philpott, the machine became the Finning Tank Drill. At least 500 were built, many of which are still in service. The original Finning Tank Drill was replaced by the M32F and M40F Tank Drills, which used larger Sherman tank carriers. At Amsterdam Airport Schiphol in the Netherlands, at least two refurbished M4s were used by the airport fire brigade in the 1960s and '70s.
