Go to the DMV office and see if there is a lien on record with the DMV. If there is, it doesn't matter that you think you have a clear title.

If there isn't, the lender's lien might operate as a matter of law, not by contract. The lender might still be entitled to the truck if you discharge the loan. Your lawyer ought to be able to figure that out. If he can't, the safest thing for you to do is reaffirm.