Is it really better to check your transmission fluid while the engine is running? If so, why? If you don't need to have your vehicle running when you check your oil, why the transmission fluid?
Good question. I don't think we have ever checked mine when it was running. I do think we checked it when the car was just shut off - so still hot. I'm not sure why though. There has to be a good reason.
It's probably best to consult the owner's manual about this. I have never checked mine while running. Maybe hot, but not running. When in doubt, I always ask my mechanic.
I am not sure why you are supposed to check it while it is running but, my grandfather who is a licensed mechanic told me that's what you do, so I do. That reminds me, I need to check mine soon.
I don't think I have ever checked the transmission fluid while it was running, but I have been told that you should check it while it is warm. I'm not sure why, but that is what I was told.