1) That don't make no sense. If the heat's building up in the gears, it's going somewhere eventually (unless you're only talking about a brief run).Why run synthetic when it doesn't pull heat away from the gears? The diff feels cooler because of it not pulling heat away.
X2plain old 80/90 is all you need.the oil doesn't keep them from breaking.
Problem is you're reading a manual for an Application that you don't have.thanks for the comments, i was just wondering about it because dana lists 7.17s as for "industrial use" so I was thinking is a d60 came in an industrial vehicle would the manual say 80/90?