jack up the rear, remove tire, then brake drum, If 1/2 ton, then remove backing plate and outer part of axle. You should see the broken part of the axle inside the tube. (assuming it broke towards the outer end, mine have in the past) take a piece of wire and tie a loop in the end, you should be able to put that around the axle (pushing it on with a long screwdriver or something) and pull it out.
Some GM axles have C" clips on the inside, and you must remove the center pin out of the spider gears first. I am not sure what you have for a rear in yours.
