Toyota Kluger 2008: Steering knock

At 120,000 km knock has developed in my 2008 Toyota Kluger on turning the steering wheel. It is not consistent and cannot be produced by oscillating the wheel. It is most annoying and I'm wondering if you have heard of this? My Dealer said it may be the steering shaft and I would have to leave the car with them. A new shaft is about $600, so I'm wondering how often this may happen again and the dealer says they can't help because it's out of warranty. What do I do?