I just did mine last week. Diff fluid dosnt ever need to be changed unless it has moisture in it according to Ford. Mine was low so I just changed it. There is a metal tag on the diff that has the oil needed for your diff. I used the Ford oil & friction mod. I put Royal Purple automatic fluid in the tranny. It can used in place of MERC or MERC V but DONT MIX W/ MERC V. Shifting is smoother w/ the Royal purple, I was surprised.
If you lift the car from body you can pour the diff fluid in right from the bottle. If you lift from axel you will need a fluid pump. USE JACK STANDS! DONT SPILL THE FRICTION MODIFIER, it will stink forever. Mine took 2 quarts, add friction mod 1st & when you are close to the end of 2nd quart, slow down because it will fill suddenly & ooz out & stink when diff gets warm.
To fill the tranny you can use the fill hole on side of tran or take off the shifter & pour it in there. You can get a fluid pump w/ a plastic tube to pump it in the fill hole from Autozone for about $10. I used the shifter method.
Get the "one minute" gasket compound for diff. It comes in a little "cheese wiz" style contaniner & you dont have to wait an hour to add diff oil.
