There is usually some confusion when referencing Ariens made gearboxes. The terms aluminum and steel are used to differentiate between the two types. The housings are different but it is what is inside that makes the difference. If you do not know what is inside you are left wondering why an aluminum case is better than a steel case (case iron).
The terms used of steel and aluminum are used to distinguish between the better quality gearbox (steel) versus the lesser quality gearbox (aluminum). The quality connotation includes the material used in the gearbox but the real meaning mostly refers to the internal components. Below is a link to exploded views of an aluminum and cast iron gearbox.
It’s easy to make a very strong gearbox of aluminum as Toro has done. That is nice but it is what is in the Toro gearbox that makes it a good gearbox. By the way the Toro aluminum gearbox is much thicker than most other companies gearboxes (MTD, AYP, and all others that I know of).
http://www.kedawei.com/Doc1.doc
