Trying to avoid going to court

I got divorced a year ago. We went through the process just fine. When we were together all of the bills and everything were in both of our names the whole time. I moved out in March 2017 and he lived in the house we were renting till the end of July and then he moved out. but now here is the problem. When I moved out he didn't let me take either one of the vehicles we had, I only wanted mine anyways and he refused so I didn't fight him over it. but now All of the bills that were on while he lived there he never paid, so the defaulted on my credit, and my vehicle he sent back to the bank and defaulted on the loan since he wouldn't let me take it.. Since everything had mine AND his name on it shouldn't he have gotten joint debt from them? I went this past week to get a vehicle but I can't now because I have $18,000 in debt on my credit from the bills he let pile up and then defaulting on the car loan. How do I fix it without having to go back to court and fight him for joint debt?