On the Diff casing then? I was looking at the top of the casing....jrm81bu said:Look at the front passenger side above the large rib. You will see a plug that a 3/8 drive ratchet will fit into(may want to use a short extension), that is the fill plug. Add until it's level with the hole, or until it starts running back out lol. It will take about 2 qts of gear oil and one tube of limited slip additive if you have a posi rear.