Originally Posted by WindKnot
The FSM calls for 80wt GL-4 in the transmission & transfer case. Differentials are 80-90wt GL-5 for open, & Trac-Loks want 80-90wt GL-5 LIMITED SLIP. Personally, I would NOT use a GL-5 oil where GL-5 oil is called out. GL-5 has a higher sulphur content which will attack brass components. A differential has no brass parts, so the GL-5 is useful. The oil weight is probably fine. Worry about the additives.
I saw most people recomending the 75w-80, but I couldn't find any...it's just crazy how different this stuff can be when it looks so similar...