Getting His Name Off The Car Title

I am wanting to pay off my car, but my ex husband’s name is still on it. I would like to take his name off the title before paying the car off. Does anyone know how I can do that? Our divorce agreement stated that I would get to keep the car and that I would be responsible for the payments. We’ve been divorced for about two years now, and as shallow as this sounds, I hate the fact that I make all the payments on time and it’s potentially positively affecting his credit. He left me with so much debt that I had to work through myself, and I don’t want him to feel like he can just benefit from my work. I am in TN and need to know if I have to have him sign anything or if I can do it without his knowledge.