The T26E4 was a heavy tank armed with a high velocity gun to counter the firepower of the latest German heavy panzers. With the T26E3 Pershing ongoing for serial production, the Ordnance Department had authorized a diversion of 25 T26E3s from their original configuration to mount the latest anti-tank gun in development, the 90 mm T15 L/73 high velocity gun. The first temporary pilot of the vehicle, designated as Heavy Tank T26E4-1 “Super Pershing” was sent into combat in April 1945. Using the earlier T26E1 hull, extensive modifications to its fire control was required due to the turret being originally designed to mount the shorter 90 mm M3 L/53 cannon only.
A 90 mm T15E1 with single piece ammunition was hastily installed on the first temporary pilot T26E4-1. Because the gun proved to be too heavy for the tank’s size, the hull was heavily modified, requiring two large equilibrator springs mounted externally on top of the turret to control elevation of the gun. To balance the extremely heavy barrel on the front, a large counterweight was welded at the rear of the turret. Other modifications involved the installation of heavier elevation gear, turret traveling and turret ring locks, and the gun cradle. The second temporary pilot T26E4-2 retained all the modifications of the first temporary pilot, but had now used the hull of the T26E3 instead, and mounted a 90 mm T15E2 with separate piece ammunition.
As the T26 turret wasn’t clearly designed to adapt the 90 mm T15 gun, additional modifications were authorized for a proper production T26E4 by incorporating a hydropneumatic equilibrator mounted internally within the turret to replace the external spring equilibrator and rearranged ammo racks. This production version would later be applied to the remaining 23 T26E4s. However, as many modifications as there could be, the T26E4 turret remained the same as the T26E3 turret by design. It still couldn’t wield such a long-barreled cannon effectively without some reliability issues.
In a parallel development, the Heavy Tank T32 was a project that came out of the successful combat use of the M4A3E2 assault tank in 1944. Intended to bolster the assault tank concept even further, the T32 would feature even more reinforced armor than the T26E3. The heavy tank was to be armed with the same 90 mm T15E2 high velocity cannon found on the T26E4, albeit with a bigger hull construction to accommodate sufficient space for the gun.
With the construction of the T32 underway, it was soon considered that the turret of the T32 could be better adapted for the long-barreled 90 mm than with the turret of the T26E4, since the T32 was already designed to use the 90 mm T15 gun from the beginning. In addition, the turret ring for both tanks had the exact same diameter of 69″ (1.75 m). Therefore, the decision had been taken to mount the T32 turret on top of the T26E4 hull. As a result, the estimated weight of the converted tank would likely increase from 94,000 lbs (42.63 tonnes) to 108,000 lbs (48.98 tonnes). It was also looking to release the final drive ratio of 17/76 for the T26E4(T32).
Although the T26E4(T32) was planned, there was no further information on whether this project was actually carried out. Further hints indicated that this was just a one-off suggestion to criss cross both the T26E4 and the T32 projects… As a matter of fact since both heavy tanks shared many similar components, the remaining T26E4 would enter engineering trials post-war and be used as a target practice for anti-tank munitions. None were described as using the turret of a T32 heavy tank. The T32 were only produced in small quantities of just 4 units, with no sign of their turret ever diverted into a different tank.
The projected tank would more or less look like this: