differential problem

[howellma]

Hi, I just bought a 2004 mercury mountaineer, v8 awd with tow package. When towing my camper, Jayco 3400-4000lbs the front differential blew oil out the vent. we basically had to rebuild the bearings in it. Once rebuilt, we drove two hours to retrieve my camper, it did the same thing bringing the camper home. I am running out of thoughts. Would appreciate any help on this.

 

[JDraper]

What are you using for fluid in the front diff and how full did you fill it?

 

[howellma]

front differential

i use 80w/90 per the manual. I only fill it till it runs out the hole. Specs call for 1.75 qt

 

[jrford]

did you rebuild the old case??? if you did then i bet its fubar. . .
i fill it to the fill hole, i have used 80-90w syn as in the manual. But i have read on on the web that the only reason is to save on cost, its half the price of Full Syn of 75-140w which is what i use in Front, now. Swap it out the rears every once a year because i tow a boat and the rear axle sometimes get submerged. . .fronts about every 30k on full syn.