There were two types of crankshafts. In the early cubs say about very early 47 IH used a forged steel crankshaft. It was prone to braking at the center main. . I H recalled all the forged steel cranks. But that doesnt mean they all got replaced. All the specks were the same as far as the journels. I have run into a few of the forged steel cranks still going strong. I have a 57 loboy that has a steel crank. It is used hard. I suspect the reason for the steel crank in my 57 is it was rebuilt at sometime with a crank out of a early cub. I have had many power unit engines over the years.I have yet to find a steel crank in any of them.
Collector of Farmall cubs and cub cadets.Injoy helping people keep their cubs running. Years of experipnce.