As the title says, replaced the transfer case fluid on my 2011 F159 today. Factory spec is 100-150k miles, this is the first change at just short of 100k. Fluid didn’t seem grossly out of viscosity but was grossly contaminated with grey goop/particals and possibly some moisture. Ford specs a “transfer case fluid” now that mercon is no longer officially produced so I don’t know if they are using anything fancier than the old mercon but I am certainly not impressed. Put Amsoil multi vehicle atf in and plan to change every 30-50k from here out.