I just noticed a whining noise coming from the rear of my 05 fx4 as I was driving. I jacked up the rear and put it in gear and got the wheels rolling. I found the noise and it was coming from the diff. and i could feel some vibration. Does this mean my gears are going? I have a little over 71k on and im the second owner any advice would be greatly appreciated

 

They have a rep on being chewed up. Search around the forums.

 

Hey, my 04 fx4 did the same thing , but it was partly my fault for running with a blown axle seal and low gearoil. 60k or so was when I had the swap done. Replaced everything except the axle shafts. The mechanic said the gear looked good, but you could see how scored the bearing race(s) were. It was his belief I probably would have returned to quiet with new bearings all around without replacing the gears. It was loud, like blower on motor with gear drive loud.

If you do need to get the work done, start shopping around now for parts and that guy, because it wasn't a cheap fix. I saved a little by gathering the parts myself,learned a little too. Ford has a TSB out but I was out of warranty. A lot of their stuff has had this axle problem. Do the forum search. Good luck.