The T67 Gun Motor Carriage was the third step in a series of designs that led to the M18 76mm Gun Motor Carriage 'Hellcat' and was armed with the same 75mm gun as early Sherman tanks.
The first in the series was the T42 37mm Gun Motor Carriage. This was designed by General Motors and had a lower profile than the M10 GMC, which was based on the Sherman tank. Work on the T42 began in December 1942. This was followed by the T49 57mm Gun Motor Carriage, a similar vehicle but with a 57mm anti-tank gun. Work switched to the T49 in April 1942 and on 18 April two pilot vehicles were ordered. The first was completed as a T49, and went for tests in July 1942 where it performed well.
In the summer of 1942 Army Ground Forces decided to withdraw the 37mm and 57mm guns from the tank destroyer force. In July General Bruce, commander of the Tank Destroyer centre, asked GM to produce an upgunned version of the T49, using the second pilot vehicle.
They responded with the T67. This carried the M3 75mm gun that was also used on the early M4 Sherman tanks, and had Christie suspension. The T49 had 7/8in (22mm) of armour on the turret, hull front and sides and 3/8in (9.5mm) on the top and bottom. On the T67 the frontal armour was increased to 1in (25mm), top and bottom armour was also thickened but side and rear armour was made thinner. Power was provided by two Buick petrol engines which provided a total of 330hp. The drive wheel and transmission were at the rear. The T49 had carried a hull machine gun but this was removed on the T67.
The single T67 underwent tests at the Aberdeen Proving Ground late in 1942. Once again the vehicle performed well, but once again the Army decided it wanted a more powerful gun. In February 1943 Tank Destroyer Command asked that the 75mm gun be replaced with the new M1 76mm gun.
This final pilot version of the vehicle was given the designation T70 76mm Gun Motor Carriage. This had torsion bar suspension and was armed with the 76mm M1 gun, which had been developed in an attempt to produce a lighter gun that could fire the standard 3in anti-tank shells. In February 1944 the T70 was standardized as the M18 76mm Gun Motor Carriage. It was given the name 'Hellcat' by the Buick Motor Car Division, where production began in July 1943.
Engine: 330hp twin Buick engines
Length: 17ft 10.5in
Width: 8ft 9.75in
Height: 75 0.25in
Top Speed: 51mph