Front Differential Overheating

[howellma]

I have a 2004 mountaineer with 4.6L and AWD, 3.73 gears. I have rebuilt bearings in front diff twice and now replaced. The front diff overheated and boiled the oil out the vent tube when pulling my camper (3400 dry)( at 70mph) Now that I have replaced it with an 06 model with 40K miles, what should I expect the temperature to run. Have not pulled it again but will try next weekend. Should I limit it to 55/60 mph to keep heat down?

 

[BrooklynBay]

Are you using the correct fluid in the differential?

 

[howellma]

yes,
used the fluid as called out in the owners manual. However, on advise from my gear shop have upped to 140 oil in front, same as rear in the current differential