Generally, there is language in the divorce documents regarding this exact situation. An attorney would have to review your divorce documents to determine what your rights are and if you can just take the car from him, which is likely not the case and I do not recommend doing so without speaking to an attorney first.
You should consult an attorney for advice regarding your individual situation since every case is different and not all information is relayed in an online question. The Law Office of Ophelia Bernal-Mora, P.A. is a family & criminal law firm located in Orlando, Florida, we invite you to contact us and welcome your calls at 407-377-6828. Contacting us does not create an attorney-client relationship. Please do not send any confidential information to us until such time as an attorney-client relationship has been established.
You should not take the vehicle from his possession, unless you meet with an attorney to discuss this issue. If you do so, your ex-husband may report the car stolen, and that won't help anyone. You should see an attorney to review your possible remedies, which MAY include (but meet with an attorney to verify you can get) damages for injury to your credit, indemnification, and possibly contempt and attorney's fees.
My answer is based upon the limitations you have given in your question, and may not be complete as there are numerous exceptions to every legal claim which requires a full analysis of the facts and circumstances of your case to discuss in detail. Please see a lawyer in your area and do not rely solely on any answers you receive from this web-site.