when it came time to service the rear diff in my rig i had a problem with the plug on the side of the housing, it wont come out! Without the resources to get a cover with a plug in it i realized that i could re-fill the diff housing through the vent tube! That is what i did using a hand pump style bottle from the local auto parts store for the gear oil, just pull off the vent line from the housing and stick on the hose from the bottle and fill it up it will go kinda slow be ready but it does work. I put about 2 1/2 quarts in it and i have not had any problems at all, this was about 6 months ago. Also for the cover gaskets i use hylomar it is available at parts stores run it on both sides of a stock gasket (yes use a paper gasket still) in a thin coat and you shouldnt have any problems, i havent at all and the cover was easy to get off still when i changed out my front again (new cover). Hope some of this info can help someone else out thanks <font color="blue"> </font>