What happens if my father passed away with no will and I cannot afford his truck?

There are too many unanswered questions. IF you do not want the truck and have not signed any papers, turn the truck over to the company that holds the lien. You are not personally liable for the payments unless you agreed to be liable. IF there are other heirs, offer the truck to them. Same with the house. Title passes to you on death. But you did not sign for the loan. To avoid liability for ownership of the home, a formal disclaimer will void liability to the local units of government.

If your father is not married and you are the only child then You are the sole heir. You should open a probate to transfer ownership of your father's assets to you, including the truck and house. If you cannot afford the payments on the truck and the truck value exceeds the loan then sell the truck and pocket the proceeds. If the truck value does not exceed the loan then turn the truck over to the lender you have no personal liability on the truck loan and no reason to pay the truck loan unless you want to use the truck.

I think there may be a lot more to address than affording a truck. I?m guessing there are payments due on it, but not on a house addressed in the details but not mentioned in the question. You should really go through everything in detail rather than addressing one question where the answer may depend on all the other facts.