gear oils are desinged to be used in gear boxes, transmissions and differentials... the biggest differences are the viscosity, its ability to maintain viscosity and withstand extreme pressure from hypoid gears, syncros, clutches and viscous couplings etc etc.
The reason light gear oils are better then engine oils is the viscosity and roping affect . because the transmission is not under pump pressure it relys on its lubrication from picking up oil the the bottom of the gears are sitting in and distributing that throught all the components without flining off... has anyone ever seen the lucas oil additive displays at napa and other auto type stores? thats what gear oils do. better protection, better clutch performance etc....
not all gear oils are made the same, nome contain molly and teflon etc....stick with the true synthetics like the Amsoil severe gear 75W-90
The great thing about this oil is you never need to change it.
because its a true synthetic water will not mix with it, so simply drian it, filter it through a coffee filter and re-use it over and over and over. the filter will remove any water and grit and your ready to reuse the oil.
think about it is big rigs can run this in limited slip differentials for millions of miles without changing it, the lil blaster aint gonna wear it out.