Huh, I'll have to give that a try sometime. I've heard of guys adding ATF to diesel engines to help bring life to bogged down engines.
I've recently read of an acetone / ATF mix that's supposedly great as a penetrating oil like PB, so you might even want to give that a try. Seems like it would be real bad for a paint job either way though, so you might want to stick with something store bought if you're trying to keep a pristine paint job.