Usually a defaulted car loan results in repossession. Go to court. Offer the judge documentation of your efforts to resolve the matter as well as solid reasons for the problem.
If you can not convince you car loan company to settle with you out of court there is nothing you can do but go to court and defend yourself. Legally they don't have to settle with you.
It seems like in this day and age no one wants to compromise. You've done the first step and tried to negotiate but they won't listen. The only thing you can really do is pay your loan on time or they will take you to court. You could go bankrupt before they sue you if needed.