Not judging, just informing. Royal Purple is no longer what it was when the oil guys loved it, neither are some other oils uhum. As for a RP in diffs and tranny's, just don't do it. The engine application is very forgiving, you can get away with a lot, but the diffs especially will weed out gimmicks, and you wont like the lesson. Internet your rp in diffs and damage, and read. You can't even mention royal purple in the 4x4 forum I'm on, it was the suspect in way too many fails. Yes it is a 4x4 forum so **** breaks, but not like this. All I have past that was at one point 6 cam fails in a row were non moly oils, 2 RP, 2 valvoline, and I forget the other two maybe some other guys remember. If you guys want to run RP or any non moly oil, consider dumping some biogaurd moly treat down there.