The rear is either a d35 or d44 (probably the later)
If your jeep is still new enough then there will be a white sticker on the axel tube indicating the model. Otherwise, easiest way to tell is the shape. If it is round it is a 35, if it has a flat top and bottom in kind of a "wedge" shape then it is a 44.
You can tell the gear ratio by a little metal tag that should be on one of the bolts but if it is an auto I think they where all 4.10
Here are a couple pics I found from google, these are not from a JK but the shape is the same. Our D44 does not have a fill plug in the cover: