I have a 2004 Excursion, and when I make slow tight turns I can feel a slight chug in the front end. It feels like it does in 4 wheel drive, but not nearly as bad. Researching this issue on this site, I think that the hub locks are either locking when turning, or just not unlocking all together. I pulled off both Hub Locks and inspected them. The left one had the switch cap fall off, and I noticed that a white plastic piece behind the switch was broken. My question is, if they are pulled off and selected to Auto, should they be able to freely rotate, or do they need vacuum applied to them to freely rotate. After I put the cap back on the left one, it allowed me to freely rotate the internal gear when I switched it to Auto. The other Hub will not unlock no matter how many times I switch it from lock to auto, but again I had it off of the wheel and I do not know if it needs vacuum to unlock the internal gear?