Have issues with with the auto locking (IWE)hubs. I replaced both hubs and vaccum cylinder(on the firewall. How much vaccum should I have going into the hubs? I still have the grinding noise in 2 wheel drive in both wheels. I think there is not enough vaccum at the hubs. Also I replaced the CV joint on the Drivers side now in 4 wheel hi there is a vibration in the front end I think the spindle going into the differential is not seated properly?? Can some one help?? (This is a 2006 XLT model)

 

Next guess, and cheaper to start with, would be to check the actual vacuum lines (for cracks/leaks) and check valves (for proper one-way operation).

http://www.ford-trucks.com/forums/12...l#post12662529

http://www.f150forum.com/f72/how-dia...m-esof-186872/

http://www.ford-trucks.com/forums/83...then-some.html

 

While the truck running jack up the front and spin each tire to see if the axles spin. If the shafts don't spin at idle they shouldn't while driving.

Why do you think the spindle in the front differential isn't seated properly?

 

One of my lines had a hole in it, I would check your lines. Rent one of the vacuum testers for free from autozone and check each side at the end of the vacuum line that goes into the hub. If you lose air, in either side that means that line is bad and track down the leak.