1995 ford f-150 rear end fluid fill?

looking at the Rear end where the drive shaft connects to the yolk on the drivers side is a square i think its a 9/16 it looks like a pipe plug Remove that then add your fluid in that hole and when it starts to dribble out that hole Put the plug back in it and your done Its only supposed to be about half full How to check is where the plug is , and when its out Take your index finger put it in the hole if fluid is touching the bottom of your finger its fine dont add if it does not touch your finger ( the gear oil ) Then add until it dribbles out

Because they are never filled all the way up to the top, look for threaded plug about half way up. Usually flush fitting pipe plug, meaning it could be recessed. Maybe a Allen wrench style or a 1/2" square drive style.