Which rear differential oil is currently recommended for 9.75 inch standard diff on 2001 Ford Expedition

originally, Ford recommended 75W-140 synthetic. My Ford Master Tech. Friend says it is better to use 80W-90 regular diff. Oil because 75W-140 gets too thin in use. Have you heard of this? Which do you recommend?

Asked by for the 2001 Ford Expedition
1 answer
The safe bet is to go with the factory reccomended fluid.