If he's treating you badly because you are a woman then that's illegal discrimination. If he's treating you and the men badly too that suggests that the issue is not your sex but something else. In that case he just sucks at being a manager, has personal dislike for you (that is not based on your sex) for whatever reason, etc. If the reason is something other than your sex (or some other protected characteristic) then he's not violating the law.
In either case, you want to discuss the problems with the upper management of the dealership. If you can get a few others in the place to back you up that the manager sucks and a lot of the salespeople dislike him that might be more effective than a complaint coming from just you. Not everyone makes a good manager. So they wouldn't necessarily have to fire him to solve the problem; maybe just return him to his old position and put someone else in the management position. But in any event nothing is likely to change if you don't elevate the issue.

