If I have an unsecured auto loan and walk away from it and give up the car, other than a huge credit hit what is my liability?

Assuming the loan that you have for the car is not secured by the car, why give up the car? You can keep it or sell it to a third person and use the proceeds to pay your loan balance down.

If you do not pay your loan, the lender will most likely sue you for what is owed on it, pre-judgment interest, and attorney's fees. I suggest that you consult further with a contracts attorney about your matter.