CJS F-1

i had a loud noise comin from the front of my 05 xlt 4x4 that sounded like the front hub grinding. so i checked out some forums and they all said that its the 4x4 vac solenoid. so i changed the part and the noise didnt go away so the solenoid isn't the problem??? anyone have any ideas i think it just might be a a leaky vac line in my 4x4 system... anyone have any thoughts???