Why was the M551 Sheridan called the aluminum tank in Vietnam?

Answer 1

Because it was made of aluminium, which is a much lighter metal that allows the whole thing to be airlifted using a mighty Bell UH-1.

Oh, and by the way. Viet Nam and WWII are different wars, so be careful with your category choices.

Answer 2

The US Army was shying away from light tanks after the Korean War. But with the advent of the USSR's PT76 amphibious light tank, the US Army half-heartedly wanted to counter it...with it's own version (the M551 Sheridan). Although advertised as an "Armored AIRBORNE Reconnaissance Assault Vehicle" (notice the word amphibious is missing), the real goal of the US Army was to have a "swimming tank" (amphibious) due to the massive number of rivers located in Europe (in the event of the famed Fulda Gap invasion).

As it stood then, US tanks had to crawl along the bottoms of rivers and lakes using a snorkel for the engine and crews to breath. A swimming tank would remove those troublesome snorkel installations.

As stated above, the US Army "reluctantly" went ahead with the "light tank" program because the US Army was moving towards the MBT (Main Battle Tank) and away from light, medium, and heavy tank classifications. One of the consequences of that administrative move was the categorization of the new war machine itself: it was a "Armored Airborne Reconnaissance Assault Vehicle" and NOT a light tank. The US Army has traditionally not favored light tanks...for one reason or another, preferring medium/heavy tanks. Therefore the Sheridan was nearly doomed before it went into production; until the Vietnam War and it's new ARMOR commander, GEN Abrams entered the scene. Abrams, being a tanker (from WWII) had his input during the production of the Sheridan (the aluminum tank) and it was built in about 1966/67. As commander of US forces in Vietnam in 1969, he ordered the Sheridan sent to Vietnam immediately for combat testing...it arrived in January 1969.

Abrams believed that the marshy terrain of South Vietnam would be more practicable for light armor (light tanks) than it would be for heavy armor (Patton tanks). He was correct, although the 52 ton Pattons worked just fine in Vietnam.

The Sheridans had steel turrets and 152mm cannons (main guns) but had aluminum hulls, other than burning up when hit (nearly 200 were destroyed in Vietnam), they were pretty hot little machines.