“Unfortunately, there’s really no such thing as a short sale on an auto loan.
This may not be what you want to hear, but your best option is to repair the car, continue to keep up with the payments, and then try to privately sell the car to an individual for the absolute most you can get for it.
While it is frustrating to be stuck with an unreliable car that you don’t like, your other options are worse. If you let the car go back to the bank, any chance of getting another auto loan for the next five to seven years goes out the window. This could affect other aspects of your financial situation as well.
Using the car as a trade-in could work, but you would still need to put down a hefty deposit as a dealer would likely give you way less than the value of the car. Another downside of this is that the negative equity will extend to your new car, and you will find yourself in this same situation with a different car.