On August 29, 1940, (the day after the M3 was decided to be put into production) work began on a tank that would mount a 75 mm gun in the turret.8
In March 1941 the turret was designed based on the turret on the M3 Medium.1,5 The Armored Forces Board selected the simplest design out of 5 options in April 1941.1 A mockup of the T6 was approved in May 1941.1,12 Was standardized in September 1941 / October 19416,9.8 The design was influenced by the Canadians and British as it had a resemblance to the Canadian Ram.12
The driver sat on the left in the front of the hull, and the assistant driver on the right.7 In the turret the loader sat on the left of the main gun, the gunner on the right, and the commander at the rear behind the gunner.7 Adjustable seats that could move 12 inches up and down, and 5 inches forward and backwards were provided for the driver, assistant driver, and gunner. There were 2 hatches in the top of the hull and a revolving hatch in the turret.7 There was a hatch installed in the floor, behind the driver, for emergency escapes.7
Each member of the crew was provided a periscope.7 They could be rotated 360°, and tilted up and down.7 The gunner's, which contained a telescopic sight, was synchronized with the main gun.7 Early models had direct vision slits that were protected by thick glass plates and hinged covers for the driver and assistant driver.7 After experience with bullet splash these were eliminated and replaced by periscopes.7
The commander had a periscope in the turret hatch that could be used when it was closed.7 Starting in 1944 it was replaced by a cupola with six episcopes.7
There was also a 2-way radio and interphone system.7 They were located in a shock mounted shelf in the turret bulge.7
The transmission had 5 forward and 1 reverse speed. It also had a parking brake built in. The controlled differential transmitted the power to the final drive unit, and also contained a brake system for steering and stopping the tank.
In the engine compartment were 2 fixed 10 lb. fire extinguishers. They could be operated from the driver's seat or from the outside. There were portable 4 lb. fire extinguishers in the turret and driver's compartment.
Auxiliary generator provided extra power and could be used in preheating engine in cold weather.
There were six 2-wheeled bogies bolted to the hull which supported the vehicle on volute springs. The drive sprocket was located in the front. The idlers were at the rear and could be adjusted to take the slack out of the tracks. There were 3 return rollers supporting the weight of the track. Many of these rollers were above the suspension brackets, but other models had them shifted towards the back with a track skid on top of the brackets.
In 1944 the Horizontal Volute Spring Suspension (HVSS) was phased into production. It enhanced mobility.
The driver used levers, which operated steering brakes, to steer the M4.7
The early vehicles had the Combination Gun Mount, M34, which had a shield that only protected the gun. In October 1942, the Ordnance Committee chose to use the Combination Gun Mount, M34A1. This had a shield that also protected the .30 cal coaxial machine gun and telescopic sight. It also had 2 pieces of armor that were placed beside the gun, where it met with the shield.
The tanks had azimuth and elevation controls installed so that the main gun could be used an artillery weapon. Also FM communication radio systems were installed and could be tied into any local field artillery fire control. It could often run 2,500 miles before major maintenance on the tracks and bogies.
Early models had reputation for "brewing-up" (nicknamed Ronsons after a cigarette lighter) when penetrated by antitank rounds.8 Water jackets (signified by W in model name1) were installed around the ammunition and on howitzer models additional armor was added.8 The water jackets used 38 gallons of water, that was mixed with antifreeze, and ammudamp (anti-corrosion).1
Turret rotated on ball bearing race that was recessed and thus protected from enemy fire. The 75 mm gun was turned 90° from vertical, which allowed for easy right-hand loading.
There was a elevating hand wheel for the gun.7 If the gyrostabilizer was activated, then hydraulic power kept the gun steady while on the move.7
The gunner had foot operated switches that fired the guns electronically.7
Comparison of Main Tank Armament Performance
First prototype (T6) was built and sent to the Aberdeen Proving Grounds on September 1941.1,12 It had a cast hull and an entrance hatch on the side of the vehicle which was later removed.1 There were also two additional machine guns in the hull.1 A second prototype was built.12
The chassis and power plant was very similar to the M3 Medium.11
After testing at the Aberdeen Proving Grounds in September 1941 production was immediately authorized.11 The M4 was to be merged with M3 production lines to reduce the interruption to production.11 The was facilitated as the M3 and the M4 shared bottom hulls, engines, suspension, and tracks.11
Production started at 1,000 per month and increased to 2,000 and was built at 11 plants.9 A special plant was built at Grand Blanc, Michigan just to produce M4s.9 It took only three months from when ground was broken until the first M4 rolled off the production line.12
M4 Medium Tank (Sherman I9): Standardized in October 19416 and 1,000 per month, by 1942, were to be delivered.1 Built by American Locomotive Co., Baldwin Locomotive Works, Detroit Tank Arsenal (Chrysler), Pressed Steel Car Co., and Pullman Standard Car Manufacturing Co.
Welded hull.6,7,9 Three piece bolted nose. Cast turret.6 Initial models had narrow M34 gun mount. Later production models had wider M34A1. Late 1943 hull was combination cast/rolled.
M4 (76 mm) Medium Tank: 76 mm gun replaced 75 mm in the turret. It had better velocity and thus armor penetration. 2,600 ft/sec, range of 16,100 yards, penetrate 4 inches at 1,000 yards. Gun can also be used in indirect fire mode as an azimuth indicator and elevation quadrant was also available. Water protected ammo racks installed.
The commander had a vision cupola mounted above the turret hatch. It had 6 prismatic vision blocks of 3" laminated bullet-resistant glass.
The ammunition racks were water protected and there was a traveling lock for the main armament in the front to hold it while traveling in non-combat areas.
Welded hull. Continental R975-C1 petrol.
The construction of 2 pilot models based on the M4A4 were authorized by the Ordnance Committee in December 1942. It was tested at the Aberdeen Proving Ground and at Fort Knox, Kentucky. After some modifications it was Standardized in August 1943.
Were intended to replace the M8 Howitzer Motor Carriages that were in Battalion Headquarters Companies and Medium Tank Battalions. The 105 mm Howitzer, M4, was mounted in a Combination Gun Mount, M52.
There was a partial turret basket in the cast turret. The gunner was provided a fighting seat, the commander a convoy seat, and the loader a riding seat. These all rotated with the turret. The cupola had 6 prismatic vision blocks of 3" laminated, bullet-resistent glass.
There was a floor placed over the power tunnel. A pintle was provided for towing an ammunition trailer.
Detroit Arsenal (2-9/43): 800.
105 mm howitzer installed in place of 75 mm in turret. A pintle for towing a trailer was installed.
M4 (105mm) HVSS: With new suspension. Detroit Arsenal (9/44-3/45): 841.
Tank Recovery Vehicle M32: Based on M4.9 The vehicle may be driven and the winch operated at the same time. Chock blocks were used to prevent the vehicle from moving during winching. Telescopic hold off poles were provided so that a towed vehicle wouldn't get too close during recovery. Turret replaced. 81 mm mortar to fire smoke.9 60,000 lb winch and a pivoting A-frame jib 18 feet long. 62,000 LB, 24 mph, length: 19' 1.25".
M4 Dozer: M4s fitted with dozer blades. Some had turret removed and were used by Engineer Corps.
A quote from an e-mail from Owen J. "Red Gavigan
I was commander of the first tank to land on Utah beach on 6-6-44 with C Co. of the 70th tank Bn. My tank had a dozer hanging on the front and came in damn handy then and for seven more days until we got knocked out going through a hedgerow, not to mention what we did on the beach. My CO, John Ahearn, was commander of the second tank to land. We both are mentioned in several histories. One by Marvin who is the author of "Strike Swiftly" and the other by Stephen Ambrose, author of "D Day."
First use was in Italy in 1943. Used in many locations afterwards.