I found this little write up on the net (
http://wayalife.com/?m=200512) and thought it would be of use to ajor members installting these rockcrusher diff hats.....
I copied the data from the site mentioned above for ease of reading....
As stupid as this might sound, it never crossed my mind that I should be mindful of how much gear oil I should put in my front differential after installing my new RockCrusher Dana 30 cover. I mean, I was very much aware that the fill hole on this differential cover was considerably higher than stock, but I guess I just figured what harm could it do to add more gear oil?
Well, although more gear oil in the differential may not hurt anything on your Jeep, let me just say, it sure as hell can make a big mess. As you can see in this photo, what I failed realize was that the new and higher fill hole on the RockCrusher differential cover sits at about the same height as the vent tube. And, for the most part, I suppose this would be no big deal if all you ever did was drive on flat ground, but once you get going up an extended highway incline like the I-15’s Cajon Pass, you will quickly find out why this is a bad idea.
The first thing to clue me in that something wasn’t quite right was the stink of burning gear oil I started to smell. At first, I thought it was coming from a truck in front of me but after I passed him and the stick still stuck around, I knew it was time to pull over and give my Jeep a look. From what I can tell, the ring gear inside the diff did a fantastic job of pumping the gear oil up and out the vent tube and in significant quantities too. Pouring down from the top of the breather cap, the engine fan and/or wind speed sprayed the gear oil all over my engine leaving behind a big stinking mess.
Anyway, I guess the moral of the story is, if you buy yourself a RockCrusher differential cover, please do yourself a favor and learn from my mistake…. make sure not fill up your differential up to the fill hole.