I am having an issue with my 1996 Ford F-150 4X4 Pickup with the 5.8 L engine. When I have the front hubs locked in and the truck is either in 4 wheel drive or out I drive along with out any problem and then all of sudden I get a very loud noise under the front end. It gets so loud that you would think the front end is going to fall right out from under the front end. I have had my mechanic check all the 4 wheel drive components and they all seem ok, a little loose, but nothing major. Anybody else got any idea what this noise could be?