i dont know if yours is like the 6000 series but there are three countersunk flat head screws that hold the rear drums in place on the hub. scrape off the face of the drum to see if they are there. i recall in another post sometime ago some truck maybe smaller only had two. if you have them there is no need to pull the axle unless you want to do other maintenance and inspection.
if there are no screws then you either need the correct socket to engage the hub lock nut of you can take a flat round punch and hammer to break it loose. once loose you can just turn it off. under the nut is a flat washer and the bearing adjusting nut. dont mess up the nuts if you use the punch method. my 40's drum and hub are one piece and the axle must be pulled.
