2006 Transfer Case Fluid? What kind?

Wondering what fluid I should use in my 2006 f350 6.0 tansfer case? I've got 137k miles on the truck and I don't think it's been done since the 60k service.

There seems to be lots of debate on this issue since the formulas have changed and I'm trying to get a fresh up to date perspective.

Of course, the Ford dealer recommends their Synthetic Motorcraft Transfer Case Fluid @ $8.00/qt.

Suggestions?

Thanks!