When I engage my four wheel drive on my 2003 Dodge 3500 the light in the cab switches to 4x4 OK and as long as there is no load on the front axle everything seems alright. But when there is a load on the axle and as I let out the clutch there is a terrible grinding noise and the truck actually vibrates quite a bit. Any ideas? I would like to try and fix this myself. Thanks in advance.