2003 B7500HST Front differential 90 weight Gear oil or UDT

[cmorningstar01]

Can I use either 90 weight gear oil or UDT fluid in my front differential and can they be mixed or should I drain completely and refill with one or the other

 

[DustyRusty]

Drain and refill with the lubricant of your own choosing. Personally, I use UDT in my front differential because of the cold winter months pushing snow around. I believe that it does a better job of lubricating the small moving parts.

 

[Fordtech86]

I have 75w-140 in mine