The same thing happened to me. I dont know your driving habits or if you go off road much or through mud or anything like that but what happened to mine, according to the dealer, was there was very fine dirt that made its way past the seal and caused it to fail.

I told him I took it off road often and went through creek crossings and through mud and stuff like that. He said that's not a big deal as long as you wash the mud and crap off of the drums and inside too.

I look at it like this, what a huge pain in the ass to have to remove the drums every time I go into mud but it is more of a pain in the ass to take it to the dealer and have them change the crap out.

My two cents...

-John