The class A-1 of the Illinois Central consisted of 50 2-8-4 superpower locomotives which were based on the Lima A-1 demonstrator. 50 were completed in 1926 with 7000 to 7039 having an Elesco feedwater heater and 7040 to 7049 having a Worthington BL. The IC also bought the demonstrator from Lima and numbered it 7050. The crews called them “Big Mikes” since they were like Mikados with a larger firebox thanks to the two-axle trailing truck.
But since they were based off the Berkshire's prototype, they were not without flaws. One was the rough riding above 40 mph, what sometimes even made the reverser gear suddenly jumping into the full forward position. Another problem was the trailing truck tending to derail when running backwards, what was also observed on other locomotives with a two-axle trailing truck.
In 1937, the IC had the plan to convert all its 2-8-4 into larger-drivered 4-6-4 locomotives for express freight service. So 7038 was rebuilt in this way, with the type E superheater being replaced by a type A that was easier to maintain. But due to insufficient adhesion it remained the only one. Instead, all others were rebuilt in 1939 without changing their wheel arrangement.
In this process, their numbers were increased by 1000 and the changes in the boiler were the same as in 7038. The boiler pressure was increased from 240 to 265 psi, while the bore of the cylinders was decreased from 28 to 27 inches. Additionally, the load on the trailing truck was decreased and the booster was removed. Some even lost their thermic syphons in exchange for circulators. In this form, they were retired between 1948 and 1956 and all were scrapped.
