The Tank Recovery Vehicle M31 was based on the Medium Tank M3, and over 800 were produced in 1942-45.
One of the reasons for the success of German armoured forces was their use of armoured tank recovery vehicles, capable of rescuing damaged but repairable vehicles from the battlefield. As a result many of the German tanks reported as knocked out would return to action, allowing Panzer units to remain effective for longer.
Early in 1942 work began on producing a tank recovery vehicle based on the Medium Tank M3, which then entering large scale production, but was also soon going to be replaced by the M4 Sherman.
The new vehicle was developed during 1942 as the T2. In order to save weight the 75mm and 37mm guns were both removed, as was the machine gun cupola on top of the turret and the turret basket for the 37mm gun. A new entry door replaced the 75mm gun, with a dummy gun was mounted on the door. A second dummy gun was installed on the back of the turret. The T2 retained the driver's fixed .30in machine gun, and could also carry a second machine gun on a British mount on the cupola ring.
The T2 was given a Gar Wood Model 10-Y5500 crane, mounted in the gap left by the 37mm gun. This could carry five tons just balanced by the weight of the tank, or up to fifteen tons when telescoping legs were used to stabilise it. A 60,000lb capacity winch was installed in the crew compartment. The winch cable could be used from the front or rear of the vehicle, or out of the turret hatch to support the crane boom. Extra storage boxes were installed on the front and back of the vehicle.
The T2 was standardized as the M31. It was produced at the Baldwin Locomotive Works by converting existing M3s. Production began in October 1942 and continued to the end of the war. A total of 805 were produced, including 509 M31s based on the standard M3 (October 1942-December 1943) and 296 based on the M3A3 as the M31B1) or M3A5 as the M31B2 (October 1942, August 1943 to the end of the war).
A similar conversion of the M4 Sherman produced the M32 Tank Recovery Vehicle.
A number of M31s were later converted into M33 Prime Movers, designed to tow heavy artillery.