Howling Sound From Diff Or Transmission

[cjf9999]

I have a 2000 sierra 1500 and I am starting to hear a howling or whinning noise from somewhere in the drive train. I took it in to have them check the bearings in the rear end and they replaced the wheel bearings on both sides. also they changed the spider gears in the rear end as they were pretty chewed up. Even after all that the truck still makes a noise. The trans shifts smoothly etc, and the whine seems to happen in every gear. Any ideas? This is a 4x4 z71 model.

[mi.bowtie]

Have you changed any U joints

[50usilverado]

this may sound odd but. my dad has a 2005 grand prix gt making that sound , thougt it was in the drive train, turns out the power steering fluid was low. started to thave same thing in my 2008 silverado , cheaked the power steering level , it was low , added fluid and it was gone , might be worth a try, let me know