1999 AWD 5.0 gear oil in my transfer case. What do I do?

[RMachiele]

Hi all. About a year ago I bought a 1999 Explorer AWD 5.0 from a dealership used car lot. I asked them to fully service all fluids as part of the deal. Now these are not dealership mechanics this lot is just owned by a dealer.
I just installed a used front diff this week-end and thought it would be a good idea to check the condition of the fluid in the transfer case just to see.
Gear lube came out of the fill hole. Friggin 80/90.
So, what does that do to the coupling? Why have I had no issued with this in the 35k miles i have driven since buying? What should I do?
Folks I am Sargent Schultz on this one, I know nothing, nothing.

 

[410Fortune]

flush with atf asap!!

I would drain gear lube
install mercon V, supertec will work for this.... drive for a day, drain it. Install more mercon V, drive for a day drain it
I would repeat this about 4-5 times if not more
on final fill use a good quality mercon V like valvoline or Mobil
change it once a year after this

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