If your divorce decree stated that your ex husband is responsible for the car payment will that hold in court if the vehicle is repossessed?

It will hold up in court BUT that will not stop the repossession. The lending company does not and should not care where the money comes from. They made a loan in good faith and they expect to be repaid the same way. If you can afford to keep the payments up to date you can sue your ex for the payments you make. Or have your lawyer file a comtempt motion to compel your ex to pay. Good Luck!