Hey guys, I'm intending to replace my reverse/low solenoid today but how am I to know which one in there is the one I want to change out? There are a few in there and they all kinda look the same to me.

I have chiltons and haynes manuals and they completely leave out anything about the internal trans parts. Tried google but not finding anything useful. Any help?
edit: I was also gonna change the external filter but the damn bowl won't come off, even with air tools. Having myself one of those real good times.