I am going to change the trans fluid and differential oil in my 1985 720 2WD 5 speed manual. From what I have gathered, I should use the following:
GL-4 75W90 for the transmission - 2.5 qts, roughly.
GL-5 for the differential - 1.5 qts.
Are these quantities correct? What weight do I need for the differential? Can I use GL-4 in the differential? I would like to be able to just buy a gallon of gear oil and use it for both, if possible.