I have a really basic question, can I powerwash my spare transmission with the vehicle speed sensor, starter, and axles removed? Should I find a way to cover the openings or will it even matter? I don’t want to rust out anything inside the tranny. Its a ys1 if it makes any difference. Thanks in advance.
Plug up any holes the best that you can. I’ve washed a couple transmissions but none w/ a pressure washer. Goal is to keep water out of the inside. You shouldn’t have to worry about rust since the whole inside should be pretty well covered in trans fluid. But still you don’t want water getting in there and mixing w/ the fluid. A little isn’t gonna hurt anything and will eventually get flushed out, but really do your best to make sure none gets in in the first place.
Simple green, various plastic and metal bristle brushes, and some steel wool are your friends when cleaning transmissions 
Unless you wanna take the easy way out and paint the whole thing w/ Aluma-Blast.
Have fun!
Thanks man, thats just the info I was looking for. 
I second the use of simple green and brushes. I use the same things when I wash any grimy metallic surfaces under my hood. Auto zone sells a package of various brushes for a few bucks, all the heads you will need. I also use two sponges, one with a bucket of fresh water for rinse and light scrubbing, and another bigger one to dry. You will have a lot of control over where your water ends up by using a sponge after you have scrubbed with SG. Good luck! :burnout: