rcgeezer,
yeah thats what he means..
you have to apply some greasy at the ring gear and pinion gear mesh..you know the two are always in contact and movement..as the pinion gear turns the ring gear heat is generated due to friction and everything there starts to get warmer and warmer ..the first thing that will melt is abviously the plastic ..so the diff case starts to melt and all the gear mesh is gone and so the pinion and ring gear worn out.. by putting the mobil 1 grease Racecrafter suggested it will be the best choice for less friction to be generated and so less heat and no warm or melted diff cases..