Most states do not provide for any "cooling off" period -- a time for consumers who enter into a contract to reconsider and rescind the contract -- in automobile purchase agreements. For example, when I last purchased a vehicle, I noticed a sign in the dealership's finance office stating that once the agreement is signed, it is final, and the buyer has no right to return the vehicle and cancel the purchase. Based on this fact, I think it unlikely that you will be able to force the dealership to rescind the purchase agreement unless you can prove that the dealership committed fraud by lying to you about the condition of the vehicle, significantly misrepresenting the likely finance terms, etc. The fact that you feel you made a poor decision when you chose to purchase this truck likely does not usually give you the right to cancel your purchase agreement.
Because I do not know all of the circumstances of the transaction which led to your purchase of this vehicle, I cannot tell you whether or not you have any legal claim which would give you grounds to challenge the validity of the purchase agreement. As I mentioned above, the most common claims would involve an accusation of fraud on the part of the seller, such as misrepresentation of the condition of the vehicle, or false statements regarding the loan terms to which you were agreeing. If you think that you may have a claim against this creditor, I strongly encourage you to consult with an attorney licensed to practice law in your state to determine whether or not you have a reasonable chance of forcing this dealership to cancel its sales contract with you. If your attorney thinks that you have a claim against the dealership, he may recommend that you file a lawsuit to have the sales contract declared void.
Assuming that you do not have the right to cancel the sale, once you signed the agreement the sale was final, and the lender would have every right to treat your "returning" the vehicle as a voluntary surrender (a.k.a. voluntary repossession). If that is what happens, this will likely cause significant damage to your credit rating. However, with diligent effort on your part, you should be able to overcome the effects of this derogatory item in a relatively short period of time. For more information about credit, and possible ways to rebuild your credit rating, I encourage you to visit the Bills.com Credit Help.
Again, I recommend that you consult with an attorney to discuss you state laws related to auto sales, and what rights you have as a consumer.
I wish you the best of luck in resolving this dispute.
I hope that the information I have provided helps you Find. Learn. Save.