Rear Diff Noise

[b49980]

My 07 GMC Sierra 2500 HD 4WD has a whine/whistle that appears to be coming from the rear diff. If it is a pinon bearing, this will be the second time it has had this problem.
Have been running the factory spec syn fluid.
Is there something I should be doing differently? Use of another fluid?

 

[98trck]

do you have 35's or bigger on your truck with stock gearing probably 3.73 you are taxing the whole drivetrain
you may need to go to lower gearing
on a 4wd that is no fun because you have diffs to change
PETE

 

[98trck]

do you have 35's or bigger on your truck with stock gearing probably 3.73 you are taxing the whole drivetrain
you may need to go to lower gearing
on a 4wd that is no fun because you have diffs to change
PETE

I meant to say two differentials to change