shuddering

Yes, I know there are a LOT of threads on this issue. However, I was wondering if there is a more permanent fix than just a fluid flush. Or is that the "permanent" fix? I just got an fj and it's still under warranty so I wanted to know if I should have something that costs a lot of $$$ fixed...

My FJ has 143,000 kms on it and lately there is a rumbling/shuddering sound when accelerating between 40-60 kmph. I took it into the dealership to have them investigate and they suspected that the problem was in the exhaust system with the gasket in the exhaust pipe having been worn out and not...