My wife and I are currently going through a divorce. She is currently driving a Nissan Sentra that is financed solely under my name and registered under my name. I currently drive the Honda Odyssey, which she is a co-signer/buyer. I want to switch vehicles with her... but refuses. We had a previous (verbal) arrangement prior to the divorce that she would take care of the payments on the Honda and I would take care of the payments of the Nissan... but have noticed that she has not been making payments on the Honda, and is on the verge of repossession. What do I have to do to get my Nissan back?

My wife and I are currently going through a divorce. ...

That says it all: ask the judge to award you the Honda Odyssey.

You have to get the court to put it in writing and rule on it.
Plus if she is not making the payments, it is your credit being hurt if you are alone on the credit, so you need to be paying it

My wife and I are currently going through a divorce. She is currently driving a Nissan Sentra that is financed solely under my name and registered under my name. I currently drive the Honda Odyssey, which she is a co-signer/buyer. I want to switch vehicles with her...but refuses. We had a previous (verbal) arrangement prior to the divorce that she would take care of the payments on the Honda and I would take care of the payments of the Nissan...but have noticed that she has not been making payments on the Honda, and is on the verge of repossession. What do I have to do to get my Nissan back?

You stated that she was a co-signer for the Honda - whose name is on the title?