The Medium Tank M4E5 was the designation given to two pilot vehicles for the 105mm armed version of the M4 Sherman.
Work on fitting the Sherman with a 105mm howitzer began early in 1942, and resulted in the two M4A4E1 prototypes. These carried a 105mm howitzer in a standard M4 turret, with the guns in a combination mount T70, with a 3in cast gun shield, and were ready for tests at the end of 1942.
These tests revealed a number of problems with the howitzer mount, in particular with the firing mechanism, recoil system, layout of the breech and the balance of the turret.
A series of modifications to fix these problems were approved in February 1943. At the same time the power traverse mechanism was eliminated from the design and a partial turret basket, with seats for the three turret crewmen, was added.
Two pilot vehicles, with the designation M4E5, were built in the first half of 1943, and went to the Aberdeen Proving Ground and then Fort Knox in August 1943.
The M4E5 was powered by the Continental R975 air cooled radial engine use in the M4 and M4A1. It had a welded hull, and the standard M4 cast turret. The new 105mm howitzer T8 was lighter and better designed than the earlier model, and worked better in the turret, as well as reducing the turret balance problems. The mount was also improved, and had a greater range of elevation and improved optics. The gun was standardized as the 105mm howitzer M4 and the mount as the combination mount M52. Sixty eight 105mm rounds could be carried, with 45 in floor racks, 21 in vulnerable racks in the right sponson and two in a ready rack in the turret.
The Armored Board approved the M4E5 for issue to the troops. Two versions entered production - the Medium Tank M4(105), of which 1,641 were built, and the Medium Tank M4A3(105), of which 3,039 were built.