Does anyone know what to use to clean a transmission case?I'm rebuilding the trans in my Charger and I want to get the deep oil stains out of the case. Any suggestions?Thanks,John.

A aluminum wheel cleaner for non coated wheels may do the trick if they're not to bad and the case is complete degreased
or google cast aluminum cleaner

Mineral spirits first. Then hit varnish and serious stains with toluene.

Don’t breathe the fumes.

or smoke, Toluene in model glue is what would get the glue sniffers high

Maybe that’s why I am happy when I clean cases.

I use a regular degreasser first then pressure wash all the bulk of grease and oil off. I use Zep Orange but any degreasser will work like purple power. Then I use a caustic degreasser that basically etches the aluminum and gets it perfectly clean. The best stuff was some I got from a friend who worked for a hvac company. It cleaned awesome and left the aluminum shiny. Most leave the aluminum a dull grey.
Only pressure wash a transmission if you will be taking it apart immediately. No matter how well you try to seal it up there will be some water that makes its way in.

There's a local guy that advertises Vapor Blasting for aluminum parts. The parts come out like brand new. Not sure if there is someone in your area that does It?

Glass bead/media blast always gives a nice surface look. Vapor blasting is the same process but with water instead of air.

Purple power is a strong degreaser that has "brightner" in it and i agree with Mike, its a great way to cut the lardy caked on sludge accumulate. You may have to agitate with a stiff brush after it has sat for a few minutes. Then, find a truck wash( big rigs) or similar place that will sell you straight wash acid. It will disintegrate any remaining grease or residue and leave a nice etched surface suitable for painting or polishing. Do not leave acidic products on aluminum for too long, they will start to dissolve the metal.

Case (and other stuff) cleaner.

LOL

I wouldn't go any near a glass or media blaster of any kind as the abrasive dust can get into the smallest openings/areas. Had a friend do his oil pan that was supposed to be sealed off. Even said he flushed it several times. Ate the bearings within 5 minutes of start up

If you want it look original in texture and finish, see if you have someone that does dry ice blasting in your area......

Nice👍

I'm pretty partial to Easy-Off oven cleaner. The yellow stuff, not the new blue stuff, though, the blue can ain't terrible.

But it had baffles. On a trans case ? I'll pass. Wonder if the OP knows anyone with a hotsy ?

I'll second Easy Off.