>>Well, I pulled it apart after I got off work today.
Very fast, so you’re competent and capable.
>>The bushing (#7) behind the thrust collar looks like it should have a shoulder on it according to the drawing. Mine doesn't have that shoulder, so I am guessing that is what the metal flakes and chunks are that are embedded in the grease of the gear box.
Yep, and also a flat on the flange(shoulder). Check the case halves as there should have been a flat step molded into the case halves for the flat on the flange bearing to rest against. I’ve seen the step worn away.
>>The grease seems to be kind of heavy for a winter gear box, especially since I live in one of the coldest spots in the country.
Was the grease spread against the case and not lubing? Generally the grease type is selected for preventing leaks as opposed to any superior quality in the grease for lub’ing. They are all EP and lub well enough. You could use an EP 00 or something more liquid in cold temps like Ariens L2 (good) or L3 (better). When you put it together you can get a new gasket if used or they may call for something like loctite liquid gasket. Anything will work well enough when new for sealing. You can add Permatex or loctite to a paper gasket for insurance against leaking.
>>Other than the bushing & gear box gasket, are there any other parts I should replace while I have it apart-seals, etc.? The worm drive/gear look like they are in good shape.
Give the worm gear a very close check. If deformed it can go through a gear fairly quickly.
I’d be a bit nervous if I could not come up with a reason for the condition of the back flange bearing wearing like that. It could have gotten nuked because something else was loose then putting force on the bering’s flange and case step flat. It should not have been turning because of the step and the flat on the flange of the bearing. What else moved before that?
Possibly it could have worn by strong pushing of the flange flat against the step flat. Something might have caused pinching or binding of the drive shaft to the inside to the flange bearing, grabbing it and causing it to wear into the step flat by force from the drive shaft directly.
Again, I don’t see how you can have just a worn flange without damage to the step flat molded in to the case. That’s the only thing it could have hit if everything else was ok.
Is the collar dowel pin ok? Seems like there should be collar damage or at least severe scratching on one side from the flange.
>>Any recommendations for a mail order parts store? Thanks for the help.
Some places have some parts cheaper but others other parts for less but paying multiple shipping charges wipe things out. You can google each part number and get prices for whatever you need. The flanges, collar, washers and seals will be cheap. The worm and gear pricy.
You’ll be ordering parts so have a week to think about how it got like that before assembly.