This spring my 2007 (155K) started getting a bit noisy when turning and parking. The noise is underneath, low frequency and can be felt in the steering wheel and pedals. Later this summer I noticed when driving down steep hills and braking near the end (15-30 mph) the vibration intensified quite a bit along with the sound. Yesterday, I noticed a light vibration in the floor and steering wheel while on the highway for 1.5 hours, at 60 or higher. The odd thing - it lasted for 5 seconds, then stopped, and repeated every 10 seconds. In other words, every 10 seconds, it vibrated for 5 seconds the entire time. I'm convinced it's in the driveline, possibly related to the AWD system as they can get stressed a bit from tight turns, but also see common issues with the torque converters mentioned here. Would it make sense to change the transmission fluid? It's been done maybe 2-3x. Are odds good that an expensive part is failing? Should I see a transmission specialist or dealer? I need to take it on a 1200 mile trip in a month, and is that a bad idea? Thanks!