If you own both the trucks and the S-corp and control both, it is unlikely that leasing them to the LLC will protect you. Because this is not an arms length transaction, someone suing due to, say, a truck accident could most likely "pierce the corporate veil" of the LLC by convincing a court that the transaction is a spurious or fraudulent one: not a real business transaction, but one intended only to defraud injured parties by depriving them of recourse. Also, that since you control and own both, you are the real party in interest no matter how you tried to structure matters.