Could be worth checking this stuff out as well ...
http://www.itwpf.com.au/molybond_lub...x?productid=69
I have used this stuff for years but in 4x4's and can say without a doubt it helps in high stress applications such as gearbox's.
Anyway could be worth checking out for yourself but I'm sure it would be beneficial to help keep your gearbox in one piece.