Welcome to the forums.
If you're talking about the rubber boot over the u-joint, there's not even supposed to be any oil in that area. Your output shaft seal or pinion seal must be leaking. There shouldn't me much pressure. Check your rear diff vent line and make sure it's not stopped up.I got doused today by a gusher of oil coming from the shaft drive boot. Is there supposed to be that much pressure in there? If so then I need to find any write ups on boot replacements.