I have a 04 F350 srw , 6.8 . Recently developed loud whine from the rear . I had the differential (10.5 sterling ) completely rebuilt . It quieted way down . But I still had a couple of high pitched whines . Took it back and had the rebuilder ride with me . At first he couldn't hear it ( it can be faint but gets louder under a load , I pull a 40' trailer and didn't have it with me), when he finally started hearing it he said it might be a planetary making a little noise , just watch it . So I made a short run (450miles RT) . Same noises but I noticed that sometimes when I stopped and got fuel , it would quiet down for 50 or so miles . I got to thinking maybe it could be a rear wheel bearing going bad and the sound transferring through the axle to the drive line . It only did it accelerating ( before and after rebuild ) and got louder going up a hill .
Today I drove it in to town and parked it ( still the same ) and a couple of hours later after a cold front came through ( maybe 10 Deg. temp change) I got in and the noise was about 90% gone , but at 45 to 60 mph. it vibrates . Let off the gas , vibrates ,, Put it in neutral- vibrates, revved the engine in neutral - vibrates and no change from rpm diff. . As long as its rolling between 45-60 , it vibrates . Hit the brakes- vibrates..
I have had 3 mechanics check it out ( 2 good ones and one that the other 2 take what they cant figure out ). Left them all scratching their heads .
Weved checked the driveline and I changed one U joint (prior to the short run ). All seems tight .
Anybody have any ideas ????


All help appreciated

 

Based on your description, I'm guessing pinion bearing. Or when rebuilt, the pinion bearing preload was set incorrectly.

 

That's crossed my mind , but you hate to think that . Im going to check the wheel bearings tomorrow , and try and rule out as many other things as I can before I have to take it back

 

Put it on jack stands , and ran it . Definitely coming from the pinion .

 

Glad you found the problem, just sorry it wasn't something easier to fix. Obviously I'd take it back to the rebuilder and let them see the problem. Hopefully they will take care of fixing it at no, or small charge.