Most versions of the T1 series of light tanks shared the same basic layout, with the engine mounted in the front and the turret, transmission and final drive all located in the rear.

The exceptions were the T1E4 and T1E6, which moved the turret to the middle, the engine to the rear, and the transmission and final drive to the front, a configuration similar to later tanks.

It was powered by a 105 hp (78 kW) Cunningham water-cooled V8 gasoline engine which gave it a top speed of 20 mph (32 km/h).

The 37 mm main gun was changed to a long-barreled Browning semi-automatic type, having a much higher muzzle velocity of 2,000 ft/s (610 m/s), though later the old M1918 model was reinstalled.

In some ways this was a hybrid of the T1E1 and T1E2; it had the high-velocity long-barreled Browning gun, thickened armor, and more powerful engine of the T1E2, but it retained the hull, turret, dimensions, and transmission gear ratios of the T1E1.

All previous T1 versions had a totally unsprung suspension which used multiple equalizing links between the bogies to spread out impacts from rough terrain.

The engine was moved to the rear, the transmission and final drive to the front, and the turret to the middle of the body.

The T1E4 also got a new suspension copied exactly from the British Vickers 6-Ton light tank, which the Army had recently tested.

At first the T1E4 retained the engine from the T1E1, but this proved to be underpowered, so it was replaced by an improved Cunningham V8 producing 140 horsepower (104 kW), giving the T1E4 a top speed of 20 miles per hour (32 km/h).

All previous T1 versions used a simple clutch-brake steering system which led to a loss of power while turning.

Testing showed the controlled differential steering to be clearly superior to the clutch-brake system, and the Ordnance Department recommended its use for all tracked vehicles that could exceed six mph (ten km/h).

[20] Due to that museum's closure in 2010, it has been moved to the U.S. Army Ordnance Training and Heritage Center at Fort Lee, Virginia, where it is presently in indoor storage and not publicly accessible.