Hello All. I am a newbie here and was hoping someone can answer a question or two. I own a 2003 Nissan Frontier SE 4x4 Pickup that I bought brand new. After only 12,000 miles the engine crankshaft rear oil seal started leaking. The dealer replaced it under warranty. Now some 40,000 miles later it is leaking again. They will replace under the 60,000 mile drive train warranty. What is making the seal go bad? Is this just going to happen again? Thank you.