'95 noise stops when in put in 4 high HUB???

Hi..please help me figure out what wrong with my new truck..1995 Ford F-150 XLT 4wd, 56,0000 miles. Ok, when driving down road a metal against metal sound comes from the lower front end. Pressing on brakes does not stop it. Nor change the sound of motor when gas is pressed. It will make the metal sound then a hard "clunk" and then immediatly stops. Someone said to try putting it in 4high when it does it and if it quits it is more than likely the hub. It DOES stop when I put it in 4high. I want more input on this before I spend money and it not be a hub. Is this a sure fire way to know it is the hub. I was told my truck has vaccum lines running to the hubs. Bear with me here men...I am a woman. I am upset cause I bought this truck on a Friday and it started this on the following Monday and the dealership wants to charge me just to diagnose it. It did come with a 30 day motor and powertrain warrenty, is the hubs part of either one? Thanks for your prompt reply...my 30 days are getting close.

lizzye71

The hubs should be part of the powertrain. That should include engine, transmission, driveline(front and rear axles) and drive shaft.

I would bitch like hell at the dealership you bought it from. They should cover it with or without a warranty if it happened that soon.

But bitch "nicely".