What's the diff?
I certainly agree with a couple of the latest postings. The concept that if 10W-30 oil is Good!, then 5W-50 is (somehow?) Better! and 0W-75 would have to be Best! has , I hope , already been de-bunked more than a few times...
My reading has led me to believe that a viscosity spread from 85W-140 may be needed (and spec'ed) for a mucho! higher load rated rear end, but is not required or even desirable in a car/light truck/SUV application.
If the whine goes away after a fluid change with that which is recommended you should be good-to-go for quite a while. If the sound remains, perhaps further investigation might discover the cause before it leaves you stranded
or, worse yet, needing a new read end?
Just a thought!
'91 420 SEL @ 199K, '92 SVX @ 181K, '93 SC400 @ 86K, '93 Kaw ZX-11 @ 30K, '87 F250 @ 181K , 2001 Valkyrie Interstate @ 6K, Y2K Honda NightHawk 250 with 1.5K, '88 420SEL I.@ 179K & the 2nd latest, an '88 420SEL II.@ 210K runnin' parts car, '85 F150 300/NP435