Yes, it is possible to sell a car that has a loan on it through a car selling service. However, you will need to make sure that the loan is paid off before the title can be transferred to the new owner. If you owe more on the loan than the car is worth, you will need to pay the difference before the title can be transferred. Some car selling services may be able to help you with this process, but it is important to do your research and read the fine print before selling your car with a service.