Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I posted this on GardenWeb a few days ago, without much success.  Perhaps someone here can offer some advice:

I am trying to get the Aluminum gear case halves apart on my late 80s ST824. The halves are not sealed together (all bolts securing the halves together are removed), but there seems to be something internal holding the case together.  I am not trying too hard, because the aluminum doesn't seem too robust, but there is definitely some resistance.
I remember something about driving out a pin through a drain or fill hole, but I can't see it yet.
Any ideas for direction?
Thanks in advance. At the rate I'm going, I might even be able to use this spare SnoThro this season.
Ralph

After a little more gentle prying and "stuck gasket" hint from snowman, the halves are now separate.  At first look, the gears appear OK, although it is really messy with the case lube nice and thick at 10 degrees F. 

I found what I think are two followers ( round steel "buttons") inside  the case. 

 When I clean it up a little more I will have a better idea as to why the augers and impeller rotated independently.  The original owner didn't perform much maintenance and the augers rusted onto the shaft (so much for shear pins).  I have only removed one auger so far, and that one was pretty tight. I suspect that something may have sheared inside the case but I will know soon. 

This SnoThro is a late 80s ST824 with the paint peeling off in sheets, unfortunately lots of the paint and model number / serial number label are long gone.   Any info as to the m/n of this auger assy would be helpful, that way I can go to the Parts Radar and see what parts I may be missing. 

Thanks again to all for your suggestions. 

Ralph 

Ralph that late 80's ST is built like the Pro's of today if I am not mistaken.  It would be great if you can fix it up.....

C