I don't know how this works at other schools, but at mine, it's just a waste of time to try to change grades. The only way they'll even consider talking to you about it is if there's a factual, objective error. Even then, it's extremely unlikely that they'll change the grade. This happened to my friend and while they did take some inappropriate written comments out of her eval, her actual grade stayed the same.
However, I don't think you'd be "digging your own grave" if you asked the clerkship director the reasoning behind the grade you were given. I did this on a couple of occasions when the reason wasn't immediately obvious to me, and found that people were more than willing to talk with me. I think it helps to phrase it in a way that suggests you'd like to learn what you can do to improve your performance. But I wouldn't talk to them with the expectation that they'll change it, because you'll likely be disappointed.
(I just have to say it one more time - stupid third year grades!)
