will it hurt anything to use gear oil, rather than motor oil? I just swapped in a th400/203 in place of my old th350/203, and I was told to use gear oil, so that's what I filled it with. I haven't even used it yet...do I need to drain this out, and fill it with 30wt, or will it be ok? I believe I used gear oil in my last one. it has a part-time kit in it, if that makes any difference.