To increase firepower, a new long-barrelled 90-mm gun was mounted on the T26E1 in January 1945. The prototype was designated the T26E4. Development was discontinued in January 1947 due to problems with the gun and the loading mechanism. A total of 25 vehicles had been built by that time, but never entered service.

A single Super Pershing was shipped to Europe and given additional armor to the gun mantlet and front hull by the maintenance unit before being assigned to one of the tank crews of the Third Armored Division. The new gun on the Super Pershing could pierce 13 inches (330 mm) of armour at 100 yards (91 m). The front hull was given two 38 mm steel boiler plates, bringing the front up to 38+38+102 mm of armor. The plates were applied at a greater slope than the underlying original hull plate it was welded on top of. The turret had 88 mm thick rolled homogeneous armour (RHA) from a Panther turret welded to the gun barrel covering the front.

An account of the combat actions of this tank appeared in the war memoir Another River, Another Town, by John P. Irwin, who was the tank gunner. Zaloga described three actions in his book. On 4 April, the Super Pershing engaged and destroyed a German tank, or something resembling a tank, at a range of 1,500 yd (1,400 m). On 12 April, the Super Pershing claimed a German tank of unknown type. On 21 April, the Super Pershing was involved in a short-range tank duel with a German tank, which it knocked out with a shot to the belly. Irwin described this German tank as a Tiger, but Zaloga was skeptical of this claim. After the war, the single Super Pershing in Europe was last photographed in a vehicle dump in Kassel, Germany, and was most likely scrapped.