Okay, this is a continuation of the "Front Diff and Transfer case" Thread.... Review that one to see some of my methodology, my pump, and some details...
This is the Fill Plug on your Rear Diff. Looks rusty. This is going to be fun. This picture is looking from the passenger side rear tire, across the truck, towards the driver's side rear tire.
This is another square plug, so again, use your 3/8ths drive to remove that...
Thru the magic of photography, the plug is out. What you missed were about 5 soakings with PB Blaster (all the wet stuff on the side of the diff), then some torching with a MAPP Gas torch, and then the bolt came out. Piece of cake, right?? Right...
Now, there is no drain plug on this case.
Now, this might not be "According to Hoyle", okay, so my apologies to real technicians out there... but I was shown this years ago by a friend, and if you're patient, and careful, it will work.
This is the backside of that rear diff. That bowling-ball shaped rear cover plate is held on with bolts all the way around. The bottom 5 are visible in this photo.
If you loosen (do not remove) the bottom 7 bolts, and then very carefully and gently pry at the bottom, the case will open a little.. and fluid will drain.
You do not want to jamb the screwdriver way in there. You're just cracking it open a little... there's a gasket in there that you are trying not to damage.
Like so. It was hard to get the picture, and do it at the same time, but a lot will come out when the case starts to open. Obviously, you will have your drain pan under there... and eventually, the case will be empty.
Then, retighten the 7 bolts you loosened, and wipe the excess off the diff, from the area where it was slobbering out of the case...
Having done that, you now will set up your pump again, fill this case with 75w90 Mobil 1, and when full, replace the fill plug.
This is a big case. Took me almost 6 quarts to fill it.
And you're done!
I copied and stuck both threads in the Lade forum. 
