I just found a 901 side shift w/ short gears and quaffe !!!

It was sitting in the basement of a house that burnt. When I opened it the inside
is coated with gear lube and looks fine. The plastic covers are cracked but not melted.

But the outside of the case is covered with white corrosion. Just on the surface.
(not deep like some of the mag wheels I've had)

So how to clean ? I have a bag of walnut shells .....

Your arm might get sore throwing the walnut shells at it.
Maybe baking soda blaster would work well, and can be rinsed off easy.

Just clean off the grease (if any) and don't worry about the white oxidation. If you're going to make it beautiful, you really should take it apart so nothing gets into the gear mechanism. I wouldn't even shoot baking soda at an assembled transmission.

Dont blast unless you are ready to replace all of the internal bearings. That shit gets into everything.

Wipe it down to remove as much of the snow as possible and then spray it with a wax protectant.

The penetrating oil we currently use, "Gibbs Brand", works well for cleaning mag and conditioning the surface. A bit pricey, but a worthwhile investment, IMO. Google the name for sources. I would think a couple of cans would do the job.

The Cap'n

...Just read your post, and do not want to rain on your parade., BUT you may want to consider that the case is /has been warped in the fire from excessive HEAT. consider finding a replacement case, and swap over the internals. ...If it got hot enough to oxidize (white powder) the case the rubber seals are probably fried and melted/distorted. you will probably need to disassemble it for this reason anyway. oil in the side plate bearings could be cooked , I should think that disassembly and inspection and cleaning is necessary. ensuring that you save the special gearing and QUAFE is worth the effort. IMO. Based on the assumptions of some people I quess cylinder heads do not warp, until they catch on fire, and logically neighter will a transmission.

If the case didnt burn, I doubt it is warped.

Like John said, Gibbs is another product I have heard good things about.

...previous post revised...

RE your revision:

I am pretty sure it was not the HEAT that caused the oxidation. Probably was the water and agents used to put the fire out, no? Of course anyone with any core should replace the seals. As for hot enough to gel the oil in the case, he said it looks good. Sure, it should be considered for a rebuild, but not due to heat.