I have an 05 Durango limited, the one with the AWD and Hemi, etc. I have had it for a few years now, and I notice a tick / bump kind of feeling in the steering from time to time. This feels like it is coming from the front end, presumably from the differentials. Is this normal for the AWD models? It seems to go away for a bit after changing the front diff fluid but comes back maybe 6-8k miles later. It makes me feel pretty nervous when on the highway and feel this but it has not seemed to cause any issues. We took it in and had it looked at by the dealer but they said everything was OK. I just want to make sure they are not blowing smoke. Thanks..