The U. S. Army expressed its interest to the Chrysler Corporation in the development of a successor vehicle to the M47 tank in late 1950. In order to speed up the developmental process of the new tank, it was to be powered by the same engine and transmission found in the M47 tank. However, rather than retain the external hull design of the earlier tank, the U. S. Army decided to use the elliptically shaped hull of the 1950 design for the Heavy Tank T43, which in April 1956 was designated the 120mm gun combat tank M103. Employing cast homogenous armor (CHA) elliptically shaped hull and a new hemispherical CHA turret on the next generation medium tank permitted the maximum ballistic armor protection level for a given volume of space with a minimum of weight.
With the adoption of the elliptically shaped hull from the T43 tank came a decrease in crew size on the proposed new medium tank from five to four. Done away with was the assistant driver/bow gunner’s position in the vehicle’s front hull. This position dated back to the U. S. Army’s M2 combat cars/light tanks of the 1930s. Combat experience from the Second World War revealed that the assistant driver/bow gunner had little combat effectiveness and combined with a desire to increase armor protection levels led to the adoption of the ballistically superior elliptically shaped front hull and the elimination of the position on the T43 tank and the replacement vehicle for the M47 tank.
The U. S. Army contracted with the Ordnance Development Department of the Chrysler Corporation to take the general outline of what they wanted in a new medium tank and come up with an acceptable vehicle that could then be placed into series production as soon as possible. Chrysler’s first task was to complete the detailed design of the new tank and build six pilot vehicles, five for testing by the U. S. Army and one for testing by the U. S. Marine Corps. A pilot vehicle is intended to prove that the manufacturing line works and is able to actually produce the vehicle in numbers.
Chrysler quickly came up with ½ scale clay design model of the hull and turret of what they believed the U. S. Army wanted in a new tank. The clay model met the approval of the U. S. Army on 2 February 1951. Advance drawings based on the clay model soon went out to foundries for them to make the necessary armor castings.
It took the U. S. Army until 27 February 1951, before the proposed new medium tank project was officially initiated and its characteristics outlined. The new vehicle was designated the 90mm gun tank T48 and armed with a new lightweight 90mm main gun originally designated the T139, which matched the ballistic performance of the heavier M36 90mm main gun mounted in the M47 tank. The T139 gun tube also had a quick change feature that expedited its removal in the field when the need arose. The T139 main gun was later standardized as the M41.
The T48 tank boasted two coaxial machine guns; a .50 caliber (12.7mm) on the left of the main gun and a .30 caliber (7.62mm) on the right of the main gun. Unfavorable test results soon led to the removal of the .50 caliber (12.7mm) machine gun on the left side of the main gun and its replacement with a more suitable .30 caliber (7.62mm) machine gun. The .30 caliber (7.62mm) machine gun on the right side of the main gun was replaced with a direct sight telescope for the tank’s gunner.
The T48 tank also featured a Chrysler-designed remote control machine gun mount attached to the tank commander’s cupola, which allowed him to fire his .50 caliber (12.7mm) machine gun from within the confines of the vehicle’s turret. However, reloading the weapon required the tank commander to expose his head and upper torso out of his cupola.
Testing of the T48 tanks began in February 1952 and continued until the end of 1952. Sadly, the constant perceived threat of Soviet aggression in Western Europe impelled the U. S. Army senior leadership to rush the T48 tank into series production before the inevitable bugs could be worked out of the new tank. Instead, it was decided that any needed design changes uncovered by the testing of the T48 tanks would be incorporated into the series production vehicles as quickly as possible. The T48 tank weighed in at 98,400lbs (45mt) combat loaded.
The first series production T48 tanks came off the Chrysler assembly line in April 1952. To meet the demand for large numbers of T48 tanks, both the Ford Motor Company and the Fisher Body Division of General Motors Corporation were brought into the program. Even as numbers of T48 tanks rolled off the production lines, continuous testing of the vehicles uncovered an ever-increasing list of major and minor design problems that had to be addressed. Things became so problematic with the T48 tank that the U. S. Army decided in January 1953, that the vehicle was unfit to be shipped overseas for use by our frontline units. Instead, the T48 tank was suitable only for in-country training duties, if a number of major design shortcomings were addressed first.
Early production T48 tanks lacked the track tension idlers seen on the M46 and M47 series tanks, which were located between the rear set of road wheels and the rear hull mounted drive sprockets. However, a decision was made early-on to reinstall them on series production vehicles.
Testing had uncovered the fact that the original driver’s hatch design of the T48 tank proved to be too small and made for an uncomfortable seating position for the driver when operating the tank with his hatch in the open position. To rectify this problem a new larger driver hatch was devised that was introduced into series production vehicle as early as possible.
By early 1953, production of the T48 tank was in full swing with almost 900 vehicles completed by March. On 2 April 1953, the U. S. Amy standardized the T48 tank as the 90mm gun tank M48. At the same time, the new tank was officially nicknamed the “Patton 48” in honor of General George S. Patton, however, most American tankers simply referred to them as the “forty-eights” or “M48s.” Roughly 3,200 units of the M48 tank rolled off the assembly line.
A production run of 120 early-model M48 tanks were built with defective hull armor and were designated the M48C tank and were to identified by markings on the front hull glacis as “non-ballistic training tank only.”
On 25 October 1954, the U. S. Army decided to amend its designation of the M48 tank. Thereafter, the tanks with the original small driver’s hatch and the Chrysler-designed remote-control machine gun mount attached to the tank commander’s cupola would remain the 90mm gun tank M48. However, all those tanks with the larger driver hatch and fitted with a new small turreted cupola armed with a .50 caliber (12.7mm) machine gun and designed by Aircraft Armaments Incorporated would be designated as the 90mm gun tank M48A1. The new tank commander cupola would allow the tank commander to fire and reload his weapon from within the confines of his tank’s turret. Originally referred to as the .50 caliber (12.7mm) machine gun mount M1 it was eventually referred to as the M1 cupola. Besides entering into U. S. Army service the M48A1 tank took the place of the M47 tank in U. S. Marine Corps service.
Because of the smaller turret roof opening for the Chrysler-designed remote-control machine gun mount those M1 cupolas retro-fitted to early production M48A1 tanks came with an adaptor ring.
The U. S. Army never wavered in its efforts to perfect the M48 series tanks for service use. The 104,000 pound (47mt) combat loaded M48A1 tank was soon superseded by another improved version approved for series production in December 1955 and designated the 90mm gun tank M48A2. A total of 2,328 M48A2 tanks rolled off the assembly line.
A distinguishing external feature of the M48A2 tank was a raised rear engine deck combined with a vertical rear hull plate featuring two large louvered doors that replaced the complicated grill work seen on the rear engine decks of the M48 and M48A1 tanks. This new rear hull arrangement on the M48A2 tank helped in cooling the engine and minimizing the infrared (heat) signature of the vehicle and was carried on through all the follow-on versions of the M48 series tanks.
In place of the rounded fender extensions seen on the front and rear of the M48 and M48A1 tanks, the M48A2 tank had squared fender extensions, with the front fenders extension having a horizontal cross bar added for extra strength. The M48A2 tank also featured new squared front hull-mounted brush guards around the identical headlight clusters. This was in contrast to the rounded brush guards around the front hull mounted non-identical headlight clusters seen on the M48 and M48A1 tanks.
The M48A2 tanks featured only three track return rollers on either side of the tank’s hull. The M48A2 tank weighed in at 105,000lbs (48mt) combat loaded.
A key internal improvement to the M48A2 tank was the use of a new fuel injected gasoline engine referred to as the Continental AVI-1790-8. The new engine offered increased horsepower and better fuel economy. As an added perk, the new engine was smaller than its predecessors allowing for an increase in internal fuel capacity, which extended the vehicle’s cruising range on roads to 160 miles (257km). By way of contrast, the M48 and M48A1 tanks had an approximate road range of only 70 miles (113km). Prior to fuel injected engines tank engines were fed fuel by carburetors.
Testing of the M48A2 tank and field use soon uncovered some unforeseen problems with the vehicle, which were corrected on 1,344 units of the vehicle already produced. These modified tanks were assigned the designation M48A2C. A key external identifying feature of the M48A2C tank was the deletion of the track tension idlers. An important internal change to the M48A2C tank was the replacement of the stereoscopic rangefinder as found on the M47 through M48A2 tanks and the mounting of a coincidence rangefinder in its place. The U. S. Marine Corps never took the M48A2 or M48A2C tanks into service.
By the time production of the M48 series tanks ended in 1959, almost 12,000 units had been built. Much to the dismay of the U. S. Army, the short operational range of the early M48 series tanks and their numerous design problems had made them a major object of American congressional investigations in the late 1950s.
The U. S. Army’s long aversion to employing diesel engines in its ground vehicles changed in June 1958, when the use of diesel fuel was to be allowed, if it significantly contributed to better fuel economy. This decision and the need for a new more powerfully armed tank to counter the introduction of the low-slung and thickly-armored Soviet Army T54 medium tank pushed the U. S. Army to develop a new tank as a replacement for the M48 series tanks.
In 1959, the U. S. Army modified an M48A2 tank with a new front hull configuration, a Continental AVDS-1790-2 air-cooled diesel engine, and a British-designed but American-modified and built 105mm main gun designated the M68. To highlight the improvement over the earlier gasoline-engine powered M48 series tanks, on 16 March 1959 the new vehicle was designated as the 105mm gun full tracked combat tank M60.
By the time production of the M60 series tanks tank ended in 1982, over 15,000 units had been built in four different versions, including the original M60, the M60A1, the M60A2, and the M60A3. M60 tank production was so high at this time because the USA chose to sell to foreign buyers for only £ 65,000 each (i. e. £ 6,000 below cost price) in order to maintain the production facilities and specialised work force. The final version of the M60 series tank weighed in at 114,600lbs (52mt) combat loaded. Although the M60 tank series was obviously just a product improved version of the earlier M48 tank series, they were never officially or un-officially referred to as “Patton tanks.”
Even before production of the M60 series tanks began, the U. S. Army was exploring the possibility of upgrading its inventory of M48A1 tanks with a Continental AVDS-1790- 2 air-cooled diesel engine and a M68 105mm main gun. A single pilot vehicle was modified with the air-cooled diesel engine and a M68 105mm gun and designated the M48A1E1. However, the inability to mount either daylight or infrared vision devices in the already cramped M1 cupola on the M48A1 tank put a stop to that effort. The effort was rekindled in 1961 when approval was given to upgrade 600 M48A1 tanks with new the AVDS-1790-2 diesel engine.
Instead of getting an M68 105mm main gun, the upgraded M48A1 tanks were to retain their existing M41 90mm main guns for two reasons. First, funding shortfalls made it impossible to supply enough 105mm main gun rounds for all the planned converted tanks. Second, there were still large stockpiles of 90mm main gun rounds on hand. The newest version of the M48 series tank received the designation 90mm gun full tracked combat tank M48A3 and weighed in at 107,000lbs (48mt) combat loaded.
The first M48A3 tank was accepted by the U. S. Army in February 1963. The biggest improvement that this latest version of the M48 series tank series brought to the table was its greatly improved operational range on roads that went up to 300 miles (483km). This came about due to larger fuel tanks and the greater thermal efficiency of diesel fuel.
The original stereoscopic rangefinder mounted in the M48A1 tank was replaced on the M48A3 tank with a coincidence rangefinder. The M48A3 tank also received the Nuclear/Biological/ Chemical (NBC) gas particulate unit from the M60 series tanks.
Besides 600 M48A3 tanks for the U. S. Army, another 419 M48A1 tanks were converted to the M48A3 standard for the U. S. Marine Corps between 1963 and 1965. A key external spotting feature of the M48A3 tank were the five return rollers on either side of the tank’s hull in lieu of the three seen on the U. S. Army’s M48A2 and M48A2C tanks.
Another external spotting feature of the M48A3 tanks (not seen on any of its predecessors) were the large dry type (paper) air cleaner boxes mounted on either side of the vehicle’s hull over the rear portion of the vehicle’s horizontal fenders. These were the same dry type air cleaner boxes seen on the horizontal fenders of the M60 series tanks. Prior to the addition of the external dry type air cleaners on the M48A3 tanks, all of its predecessor M48 series tanks had interior oil bath air cleaners.
An easy to miss external spotting feature of the M48A3 tank was the crew compartment heater exhaust pipe that passed through the hull roof on the right side of the driver’s hatch and extended out to the right side of the tank. This feature is also seen on the M60 series tanks. On the predecessor M48A2 and M48A2C tanks the crew compartment heater exhaust pipe passed through the hull roof on the left side of the driver’s hatch and extended out to the left side of the tank. On the M48 and M48A1 tank there were two parallel crew compartment heater exhaust pipes coming out on the left side of the driver’s hatch and extending out to the left side of the tank.
In 1967, another 578 M48A1 tanks were converted into M48A3 tanks. This second batch of upgraded tanks sported some new features not seen on the original M48A3 tanks and were therefore referred to as M48A3 (Mod B) configuration.
A key external spotting feature of the M48A3 (Mod B) tanks was a spacer ring (designated as the G305 turret cupola riser) that contained nine large vision blocks and was installed between the turret roof and the M1 cupola in order to improve the tank commander’s visibility. The M1 cupola on the Mod B configuration also came with a new bulged hatch cover to provide the tank commander with more headroom
Marine Corps M48A3 tanks had received the G305 turret cupola riser as a field modification before the U. S. Army M48A3 tanks went through the Mod B upgrades.
Also seen for the first time with the Mod B configuration of the M48A3 tank was a heavy metal gauge turret interrupting bar mounted in front of the M1 cupola. Its intended role was to prevent the vehicle commander from firing into the rear of the Xenon 2.2 kilowatt white light/infrared searchlight that was often mounted over the top of the gun shield on the Mod B configured M48A3 tanks.
Late production M48A3 (Mod B) tanks came off the production lines with an embossed X-shaped pattern on their squared front and rear fenders extensions. This was in lieu of the horizontal cross bar added for extra strength on the squared front fenders extensions of the M48A2 tank through the early production (M48A3) Mod B tanks. These embossed X-shaped patterns also appeared on the frontal and rear portions of the horizontal fenders.
Based on user feedback late-production M48A3 (Mod B) tanks came with new thicker and stronger square brush guards around the vehicle’s two rear tail lights. Another external improvement on late production M48A3 (Mod B) tanks was the welded on of a thick protruding horizontal steel bar around the top of the two large louvered doors at the rear of the vehicle hull. When early production M48A3 tanks eventually returned for rebuilding they received all the Mod B improvements and the Mod B designation was then dropped.