I have a 2005 X, 6.0 with 216K. I have an intermittent sound that that is progressively worse when I make a left turn or a wide gradual left turn. The sound is more like gears are trying to engage. I am having a really tough time pinpointing the sound, one moment it sounds like it is in front drivers side of the vehicle, the next it is middle passenger side. Speed is not a factor, although the sound is easier to hear around 30 mph. Putting the vehicle into 2 or 4 wheel drive does not make a difference. I have eliminated the transfer case as the culprit. I changed it out last weekend. I have checked the u-joints and drive lines for any looseness. Any ideas on what the issue may be?