don't use grease on the rubber O-rings that hold the diff plates. Dissasemble the diff and pull out the rubber O-rings. Clean the rubber O-rings and all diff parts with brake cleaner. Insert the rubber O-rings back in the diff. Get the diff balls out of the spur and clean them in break cleaner, clean the spur as well. Insert diffballs back into the clean spur and use only a small dot of grease on each ball. assemble diff and tighten enough to not let the diff slip on power. When you have build the diff correct the corally diff can last a few race meetings without rebuild. Too much grease will only attract dirt.
After each race meeting i untighten the differantial to unload the outer bearing. I do this to not get indentations in de diffplates or flat diffballs (when using steel diffballs) by the presure of a tightend differential when the car is stored away.