This is a question I get asked quite frequently, and here is New Orleans Bankruptcy Attorney Kevin Gipson’s take on it, which is right on point. 
Also, don’t forget, that is completely up to the car lender as to whether they will reaffirm with you.  Reaffirmation is a two way street, you don’t have to do it, and can surrender the vehicle in Chapter 7, and owe nothing… but likewise, the lender could decide that they choose not to reaffirm with you. Often, before converting to Chapter 7 from Chapter 13, it is possible for your attorney to discuss the option of reaffirming, and find out from the creditor in advance of your conversion whether the creditor would reaffirm.