If you want to lube your diffs you need to take it off the chassis and either take it apart or try to fill in the hole under it. I think the diff case is pretty sealed and packed with grease from factory so i dont think its necessary to lube them. i Have huge problems with the driving gear in the diff case.. I get like 1 or 2 running hours before they`re totally worn down.. think theyre made of cast aluminium.. has no strength at all..