Could be a few things. Too much torque and the stock/old ass shaft couldn't handle it. (possibly 10 yrs. old not up for a challenge) or the car could be too low or lowered improperly which can put an unusual stress on the shafts if not done right. Or just wear and tear. There is no life span on some parts. For instance, I had to replace my master cylinder for my brakes at 50k. Sound likely? Yeah that's what I thought...