Based on your description of your loan balance, it sounds like you got stuck with the type of loan that used to be called a "rule of 78's" or "ADD ON" type loan. What that means is the lender adds all the interest that is due throughout the term of the loan onto your principal balance the moment you sign the contract. The worst part about this is the fees can still be added to the loan if you pay late - even by one day.
For example, if you buy a $12,000 vehicle and your interest throughout the term is another $15,000 (for example), then your payments are actually used to reduce the interest first. You don't pay off any of the principal balance until the last few years of the loan. If you go to sell the car, you are upside down the entire period of the loan.
This is a completely different type of loan than the one you get from a credit union where you pay interest and principal each month (a simple interest loan). In a simple interest loan, most of your payment actually reduces the principal and the interest is a small portion of the loan. If you look at an amortization schedule of the loan you are planning to obtain, you will immediately see the difference.
How do you know what type of loan you have - read your contract before you sign it. Most 'Buy Here Pay Here' type places use these type of Add On loans. They might call it by different names, but when you read the terms you will know exactly what you are getting into by signing the contract. These type of loans are designed to keep you in debt. The best solution when you are in one: Pay off the loan and don't get another one. Don't trade in a vehicle with this type of loan. It will compound your situation - making a bad loan a worse loan because now you carry the debt from this vehicle to the next vehicle AND you have to pay the note for that vehicle too. Its a terrible cycle. I know that sounds like I am not understanding, but the worst solution is to have the car repo'ed and then owe on the loan anyway!
If you pay off this car and you decide to get another vehicle. Then go to a credit union and get a simple interest loan. If you don't qualify for it, buy a beater for cash and drive it until you can qualify for a simple interest loan or until you don't need a loan at all.
I don't work for a bank. I had one of these type loans 20 yrs ago right after my divorce and learned this lesson the hard way. I have never had one since.