I have a 2010 f150 platinum 4x4 crewcab-it is making a horrible grinding noise in the front sounds like its in the front differential it acts like its trying to engage in 4wd as your driving down the road-I replaced the evaporative emissions solenoid&check valve-no good-still have grinding problem-if it is bad differential is it cost wise to replace it or try and repair the unit and do all the 2010 f150 4x4 have 3,73 ratio or is the platinum and limited different-any help on this will be appreciated