Is that gear oil and transmission oil are the same thing?

Just to make things more confusing they have now updated trans oil to 75-90 TRANS oil. There is still a different 75-90 DIFF oil. Cause life wasn't hard or confusing enough....... Granted this is all for Eaton manuals. Don't know anything about D12's

 

Keep in mind that (most of?) the oils DD specify and approve for the DT12 is a GL-4 75W90
Drive axles generally require GL5

Do not mix things up and use the transmission oil in drive-axles, or the other way around.

 

I have personally seen what happens to an Eaton trans when gear lube is installed and man o man it is not pretty........and confusing is right. And grease is not just grease anymore either.

 

Peterbilt Dealer puts 75/90 Synthetic in my diffs and 50wt Synthetic in my 18 spd tranny. My diffs rarely ever get warm enough to read above 150 degrees. I have a lazer gun thermometer and check periodically all my temps to verify gauges are working. Tranny temp, Engine Temp, diffs temp, also check my axel hubs temps.