@doctor,
You are using a mix of GL-5 85W90 differential oil and GL-5 85W90 gear oil? I gues @SKZIC got it wrong and believes you have mized GL-4 and GL-5.
Anyhow, using GL-5 oil in a system in which GL-4 is recommended leads to severe long term damage. Severe long term damage means there will be no immediate break down. But over a period of time some very expensive repair will come up which could have been avoided if you had used the correct oil.
If you see, on the packing of GL-5 oil, nearly always differential oil is noted. GL-5 is better than GL-4. It can bear greater pressure. But it is mostly useful in final drive (differential). In gearbox, it is better than GL-4 for the steel parts, but much worse than GL-4 for the brass (or other copper alloy) parts. Therefore there will be more wear and tear of synchronizers. In the FWD gearboxes, where gear shifting mechanism and differential all are in one housing, GL-4 is used, unless the manufacturer explicitly recommends GL-5.
(Mixing two types should not be a hazard, as even in engine oil you can switch different API grades and different SAE viscosity grades without any immediate harm). You can search the net for more info on GL-4 vs GL-5.
You should soon get the GL-5 out and GL-4 in.
