Find where your grease is going man.....I heard a guy saying his prospec won't hold the oil for more then 2 days...said NO diff does....I didn't think th esame so I tore mine down that night I had plenty of oil.....but when I offered to tear his down he wasn't going to let me....I then asked a friend who claimed the same thing about his XB8 (same as my buggy).....come to find out he didn't put these little O rings behind the bevel gears in....it looks tight enough to hold oi lbut it's not....point being they should hold oil, they are designed to.....if they are not then you are missing parts or not reassembling them correctly......try using some sealant around the cup against the ring gear and pack your O-rings in w/ grease....actually I use vasoline there.....neither will affect or be affected by the oil in the cup......