First changed the trans and diff lube 18 years ago when I bought the truck. Used Quaker State 80-90 in both. Used it again when I changed the oil in the trans after doing an Okie install. Changed the diff oil when I changed the cover gasket. Used 80-90 in all cases. My tranny leaks so when I top it up I use the same oil.
Everything is fine until I started reading this thread. Its still fine but now I am questioning myself. One thing I stay away from is Lucas oil.
