I posted about our 28" Craftsman snow thrower model 247.88691 recently, used 4 winters with this one being the heaviest. Recently it broke: the impeller turned but not the augers; the advice from the forum -- which was correct -- was that the gears in the gearbox had probably stript.

I finally got the gearbox off the machine and open, and it had plenty of lubricant. I believe that the brass gear failed because it's just too weak for the load over time. It's not a good design, in my opinion. The shearpins on the auger shaft are the original shearpins; they've never broken under load. Instead the gear in the gearbox stript, which is a lot harder to get and and replace.

I've cleaned the grease and brass shavings out of the gear case using a stiff brush and old gasoline in a pan, and have ordered the replacement gear. I'm having trouble though getting all the rubbery silicon seal material off the edges of the case where they join together, and from the threads of the bolts that join the two halves of the gear case together. A lot of it has come off but not all of it. Soaking it in the gasoline doesn't help: the material is supposed to resist dissolving in gas or oil.

Does anyone have any suggestions for how to get the rest of this silicon off the aluminum gear case? What chemical would dissolve it?

Any recommendations on a good brand of lubricant and silicon for when I have the replacement gear and am putting the gear box back together?

When I get done with this I'd like to post the step by step for getting the gearbox out of the machine and back in. I tried to do it without taking things apart that I didn't have to, but it was still a big job to take the machine apart enough to get the gearbox out. Craftsman really should have instructions in its manual about replacing this gear, since it is the weak link in this machine.

Thanks.

 

I think good old scrapping is your best bet. However Alcohol can be used with some success. It may take a long time. Soak the area for several hours and then scrape.
Here is a ling that might help.

how to disolve silicon glue - Bing Videos

You mentioned the shear pins not shearing when under breaking load. Be sure the rakes are loose on the axle. Use a moly grease on them. Be sure the rakes spin freely without the shear pins.