Introducing the T88 105 mm Howitzer Motor Carriage

At the United States Army’s Ordnance Training Support Facility, located at Fort Lee, you can find the last remaining T88, 105 mm Howitzer Motor Carriage, in existence. This track is based upon the M18 Hellcat. The US Army has recently allowed for Open House events to be held the Ordnance Training Support Facility and I was able to attend the first of these.

Enjoy these photos and history. There are additional Open House days in the future so keep an eye on the Fort Lee Facebook page for details. Also, look for additional posts on the vehicles and items at the Ordnance Training Support Facility. It is quite an amazing place.

In late 1944, the U.S. Ordnance Department initiated a project to adapt the high-speed M18 Hellcat tank destroyer chassis into a mobile artillery platform. The goal: mount a 105 mm M4 howitzer to deliver direct fire support with Hellcat‑like agility. The result was the T88 HMC—an open-topped prototype that married firepower to mobility. Work began on 31 August 1944, and two pilot vehicles were completed and tested at Aberdeen Proving Ground before the project was ultimately canceled at war’s end.

Design & Features

Main Armament: The standard 76 mm gun was replaced with the 105 mm M4 howitzer, a weapon originally developed for Sherman tanks. An elevation gyro-stabilizer was added for improved firing stability on the move.
Turret Modifications: The crew layout changed—gunner moved to the right of the gun. A new pedestal mount replaced the M18’s ring mount for the coaxial .50‑cal machine gun. An emergency peephole sight and a panoramic telescope shooter’s sight were installed.
Ammunition Capacity: Stored 16 rounds ready in the turret and another 24 rounds in sponsons—total 40 rounds of 105 mm ammunition.
Chassis & Mobility: Retained the lightweight, fast M18 Hellcat running gear. Armor remained minimal (7–19 mm), trading protection for speed. Top speeds were in the 80 km/h range.

A variant, the T88E1, tested the lighter 105 mm T51 howitzer and concentric recoil system, reducing turret weight and internal clutter.

Comparison Table: T88 vs. M18 Hellcat

Feature	T88 105 mm HMC	M18 Hellcat
Chassis Base	M18 Hellcat	M18 Hellcat
Main Armament	105 mm M4 howitzer (gyro-stabilized)	76 mm M1A1 gun
Crew Layout	Gunner on right; open turret	Gunner on left; open turret
Ammunition Storage	16 turret rounds + 24 hull (40 total)	Approximately 45 rounds of 76 mm
Armor Thickness	7–19 mm	7–19 mm
Top Speed	~80 km/h	~80 km/h
Intended Role	Mobile assault gun / fire support	Fast tank destroyer
Status	Prototype; project canceled at war’s end	2,500+ built; saw combat in Europe

Role & Intended Use

Unlike traditional tank destroyers like the M10 or M18—which focused on anti-armor gunnery—the T88 was conceived as a fast-moving assault howitzer, providing direct fire support for infantry and armor in fast-paced operations. Its stabilized 105 mm gun would have been effective against bunkers, trenches, and clustered enemy formations.

Why It Didn’t Move Beyond Prototype

Development of the T88 wrapped up just as WWII was coming to a close. With the shift in U.S. armored doctrine towards multi-role tanks (such as the M26 Pershing) and the success of conventional self-propelled artillery, the T88 was no longer a priority. Only two prototypes were built—no mass production ever took place.

Legacy and Influence

While the T88 never saw combat, its concept—a high-speed chassis armed with a large-caliber gun—anticipated postwar designs like the M56 Scorpion and later Cold War SPGs. It also influenced amphibious experiments such as the T87, which used the T88 turret on a floating M18 chassis for waterborne operations.

Final Thoughts

The T88 105 mm Howitzer Motor Carriage stands as an intriguing “what-if” in U.S. armored development—a hybrid of firepower and mobility built on one of the fastest chassis of WWII. Though it never entered service, the T88’s ambition and design innovations make it a fascinating footnote in the history of armored warfare.