From the looks of it the iron gear box has more robust components and thrust bearings ( item #9, lower diagram) on the worm shaft.
The aluminium unit seems to have fewer parts.
Except that the drawing is not comparing current models. The cast iron gearbox shown
is from an old model.
If you want to compare Ariens' current offerings for their top-of-the-line aluminum
and cast iron gearboxes first go to Ariens' Parts Radar (go to www.ariens.com and
select "Parts" ).
For the aluminum gearbox enter "921004" for the model number (924DLE Deluxe),
hit "Search" then select "921004 (002001 - ) ST924DLE". Then click on
"Gear Case Aluminum" in the box on the right.
For the cast iron gearbox enter "926017" for the model number (9526DLE Pro),
hit "Search" then select "926017 (002001 - ) ST9526DLE". Then click on
"Gear Case Cast Iron" in the box on the right.
The frames of the part diagrams can be stretched to get a better view. If you
do the above in separate windows you can easily compare the two gearcases.
You will notice that there is just about no difference in the parts that make up the two
gearboxes other than the shape and material of the case (the apparently missing thrust
bushing on the aluminum gearbox is just shown at the other end of the worm shaft).
I believe that the big difference now between the two boxes is that the cast iron case
will better resist a shock if the snowblower swallows something solid.
Paul
This message was modified Dec 1, 2008 by pvrp