Hope you guys can help with this one. At 35mph to 40mph my 01 F250 7.3 has an awful whine and I can't pinpoint where it's coming from. Thought it was the rear axle outer bearing so I changed them but it's still there. My next attempt will be putting the stock tires back on it in hopes that clears it up.
I hope somebody has an idea because around town it will drive you nuts.
Thanks,

 

check center support bearing in the rear shaft or it could be your carrier bearings inside the diff maybe you will get lucky and just have to put a center support in it. hope that helps

 

My wifes rig has been doing the same thing for the last two months, its getting worse and worse...

Front wheel bearings in her case

 

Thanks ya'll, I will check out both.