I have a couple of transmissions that lived thru the barn fire
They are all black with soot ... I AM thinking oven cleaner... any other thoughts

Brake cleaner. Expect to go through 5-6 cans. Mineral spirits works great, but takes more effort. Are you planning on taking the gear stack out, breaking the box down and replacing the seals? If so, you can dip the cases or soda blast. I'd probably stay away from oven cleaner, as it may pit the box if you're not careful.

Block off the case breather with duct tape,brush non caustic degreaser on and waterblast them.
A big NO to the oven cleaner as mentioned,how these clean up will most likely indicate how hot they got,@ minimum I would replace the input shaft and output shaft seals.

Oven cleaner is fine, I have run tests with it over months with no pitting. Old wives tail. Likely the best fit for your situation. You should pull the stack and wash the cases thoroughly. If I can help, let me know. What ever I have to give is yours.

If one water blasts it and doesn't pull the stack.....the gears will rust.

Ask me how I know.

Water will get in the side seals and other parts under pressure. Pressure wash is a bad idea unless disassembling.

Ice pellet blastning should work, havnt tried it myself yet tho.

If not disassembling, slow, tedious, meticulous cleaning.

Pull the stack and diff, then soda blast. Then you only have to manually clean the intermediate plate. Plus you can inspect the internals in case something should be attended to now (perhaps something melted inside?).

Walnut

.....and bake at 450 degrees until done

Wouldn't the whole case be warped depending on how close the cases were to the fire?

Oooops, looks like I just screwed that up!



Now going to add a rebuild to my resto to do list. Had a few small random issues with first gear and the down shift to second at times, so now whether or not to split open the transmission case has just been decided.

Test ZEP 505 on small sample....

Do look for crystallization of the aluminum. Of you see this you will probably not want to bother cleaning as the case will be shot. The internals should be fine.
No point in cleaning if it's garbage.

The only reason I mention this is I was with Rob and Chris yesterday and saw how hot the fires burned, aluminum will harden, but once the metal gets too hot it's done.

Ah....the tranney case is magnesium.

I have a spare case if anyone needs one.

Ya....unless you are talking 1969 and older 911/912

Thanks Mike!
one of these trannys was rebuilt at a clinic the other was a good tranny from the 914 that burnt ... They both where out on a steel shelf a ways from the heat of the fire, there was a wooden table close by that was blackened but was not burnt.. So the order of business is just to take the black crap off of them... But I see pressure washing won't be a very good way... I dont really want to disassemble them... but we will see