Unfortunately, Skippy is right about divorce decrees and who is responsible for certain debt. The creditors don't care since the binding contract was made prior to your divorce. My advice is try and negotiate with the creditor and if nothing works out arrange a voluntary reposession so you don't get stuck with more fees like- Towing and they often use repo-men that charge a pretty penny. All these extra expenses will be added to your total balance not to mention the repo men often use "shady" tactics like entering garages etc to get the car. (I know, I worked for a finance company)
Okay so worst scenario- they take the car back, sell it for less than what is owed and you are stuck with a balance. Since both you and your wife are joint signers you should be able to split that by half for your portion- again, you have to negotiate with them first.
After one to two years it will have less negative impact on your credit report and you could even begin to dispute that this is not yours. I successfully deleted two items this way on my own report, using the divorce decree as my anchor but you should wait at least one year.