Whirring noise

[lugnut05]

A strange whirring noise developed in my 1987 Bronco II.
(5 speed,manual)

Sounds like an airbound power steering pump.
It does it even with the engine off and if I put the transfer case in neutral and roll at speeds above 20 mph. The noise picks up slightly with speed as one with suspect, but engine rpm does not affect it. IE I can downshift and the whirr
stays at the same pitch.

I did change the fluid in the transfer case when I first noticed the noise.
I found a soup of what I suspect was ATF and Hypoid. (Probably a fast lube joint topped it off for the PO.)
I am running straight Mercon ATF now, and still have the problem.

I would bet a bearing is about to fail, but curious what you think.

[rebocardo]

I think more likely the clutch disc is about to fail and you need a new slave cyl.