I use the Doo Synchromesh Transmission Syntenic Oil. Thats the recommend type of oil. Changed it 2 times now. I have 6000+ KM pulling a grooming drag for snowmobile trails. Would be cheaper to use your Oil.
The Expedition with high ,low and reverse takes a special gearcase lubricant just to let you know. They want you to take exhaust muffler out to check and fill.