It is not uncommon for ex-spouses to fail to obey court orders for turning over property divided in a divorce, but they are risking contempt of court.
Your ex wife should be following the divorce decree, which is an enforceable court order. Your decree apparently requires her to return the car to you. You have indicated that your decree, like most decrees, does not require you to refinance, or "take her name off the loan." This in no way diminishes her responsibility to follow the order of the court and return the car to you.
You may need to get an attorney to help you by filing an enforcement action. If so, your attorney can ask that your wife be held in contempt and fined, or even jailed for violating the court's order. Your attorney can also ask that your ex-wife be ordered to pay your attorney's fees. She would likely regret being hauled into court to explain to a judge why she did not see fit to do as she was ordered to do by the court.
You may also be able to have your car returned if the lawyer simply sends her a strong letter to this effect.
You will need to take her back to court. If she is worried about you failing to pay the loan, she has to wait for you to fail to pay, then sue you.
You might be able to just go get the car using the decree as the instrument showing ownership, if it lists the VIN... you would still need to figure out how to get keys and all, or switch the keys on the car. You could hire a lawyer to draft a letter to her first, and see if that gets her to move.
Disclaimer: This answer is intended for informational and educational purposes only and should not be considered legal advice nor forming the attorney-client relationship.
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