What if I bought a car in Oregon and did not pay back the full amount on the loan, only the original amount.?

Paid $3,000 down on a car, total value of the car was $9,000, so naturally the total amount left on the loan is $6,000 excluding interest. With interest, I would have to pay back roughly $7,500 back to the bank or loan company. Now paying back $7,500 over 36 months is what is set in stone on the contract. However, what if I pay back the $6,000 to the loan company over 24 months without paying them interest? I still pay them the balance they put up for the car, but they won't make any money on it. At this point, what could they do to me?