When I blew my rear diff I noticed oil had leaked all over. It seems oil was seaping out around the gasket area and the low oil probably caused the plastic gears to heat up until they stripped. I used some black gasket sealant by recommendation of my on road cars on the gasket when I rebuilt my diffs and so far so good, no signs of leakage. I also used that same stuff on my shock caps and they haven't leaked since. Looks like a $4 tube kills two birds with one stone.