Have 2005 F150 5.4L 4WD Unit is trying to engage on all left hand curves and ocasianally on straightaways, any help would be greatly appreciated, it has been doing this for about 1 month on left hand curves but just the last week on straightaways when it does it on staights you almost have to stop the tuck before it quits, has 70,000 miles and never been abused.any thoughts or ideas would be appreciated.Thank You

 

Check out the link in my signature.

Also it comes to mind when you say left hand curves, as a grinding or noise like that when turning one direction or another is usually a sign of wheel bearings needing replaced.

Read that thread in my signature and try a couple things in there. You will know pretty quick what you are dealing with. And let us know.