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The Medium Tank M4A3(76)W HVSS was the first production version of the Sherman to use a Horizontal Volute Spring Suspension system, which improved both the ground pressure of the tank and made the suspension more reliable.
The Vertical Volute Spring Suspension system used on the majority of Shermans was first used on the Light Tank M2, then adopted for the Medium Tank T5, Medium Tank M2 and Medium Tank M3, before being chosen for the M4.
The system was based around a series of bogies, each carrying two road wheels. The wheels were linked to a central strut on pivoting arms that were almost horizontal. These arms were linked to the top of the bogie by vertically mounted volute springs, which were made by winding a strip of sheet metal to produce a spring in which the coils could slide over each other. The Light Tank M2 used two bogies on each side, the medium tanks all had three on each side, for a total of six road wheels. Early M4s used the same VVSS system as the M3, but during the production run a modified version with stronger springs was introduced. Even with this change the VVSS system had two faults - a short life span and high ground pressure.
One alternative that was available was the Horizontal Volute Spring Suspension system. In this system the two road wheels were still connected to the base of the bogie by the base of an almost triangular pivoting arm. The two arms were connected by a single horizontally mounted volute spring that was carried above the pivots (mounted half way up the triangle). Finally a fluid shock absorber was carried above the spring, also mounted horizontally, connecting the top of the triangles. The two wheels on each bogie acted against each other, which helped to keep the track under tension.
The HVSS system had been considered for use on the Medium Tank M2. In 1942 two Medium Tank M3s were given HVSS. Early in 1943 one M4A4 was given the system, and in April 1943 one of the M3s and the M4 went to the Armored Board for trials. Shock absorbers were fitted on the front and rear bogies, and they used the standard 16 9/16th in wide tracks of the M4 Sherman. In tests the new suspension improved the tank's performance on rough ground, but not the ground pressure problems.
In September 1943 work began on an improved HVSS system, with a wide 24in track and dual bogie wheels. This had the pivoting arm in the centre, with a road wheel on each side, giving each bogie four wheels carried in pairs (inner and outer). This allowed the use of wider tracks, which lowered ground pressure.
Tanks with the new HVSS system were given the E8 designation at the end of their original designation. Tanks based on the M4E3 thus became the M4E3E8, and the type was known as the 'Easy Eight'.
Tests with the first pilot tank showed that the new suspension improved performance, but still lacked reliability. In November 1943 ten M4A3E8s were ordered for further trials, and these were completed by April-May 1944. These tanks incorporated a number of improvements designed to improve the reliability of the suspension.
In March 1944 the production of 500 M4A3 (76mm) HVSS tanks was approved, and at the end of the month the HVSS was recommended for all M4 production.
The M4A3(76)W HVSS also used the wet storage system developed as part of the 'ultimate' M4 design. Thirty five shells were stored in the hull floor, and another six in a ready rack in the turret floor. The shells were protected by 36.6 gallons of water.
The M4A3(76)W HVSS was built at Chrysler's Detroit Arsenal. Production switched to the HVSS model in August 1944, and 2,617 were built between then and April 1945.
At the start of the production run the M4A3(76)W HVSS featured the 76mm gun M1A1 with no muzzle break, and the split circular loader's hatch. The commander's vision cupola was introduced early in the run. The oval loader's hatch and M1A1C or M1A2 guns with muzzle break were also introduced during production. A new version of the floor escape hatch was also introduced.
As with all versions of the M4A3, this was the preferred model for the US Army, and most M4A3(76)W HVSS tanks were thus used by the Americans.