NO warranty. I tend to agree with bad initial assembly or a balance thing. The miles that this engine has were a move from california back home to michigan and I felt a steady vibration the whole way, assumed a u joint or mabye tailshaft bushing in the transmission( th350) never really found source of vibration. I removed the engine and noticed the excessive end play after I was rear ended and the truck was totaled. Now I am putting the engine in another truck and hoping a crank with new bearings and new oil pump will do the trick. I will probably also replace flex plate and check everything I can upon reassembly. What would you do if it were you?