Gear oil spraying from the shaft boot

I have been searching the site with no luck. 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. Also this was a freebie machine because they thought the engine was messed up. It ended up needing a new spark plug. I filled it with synthetic oil and filters and now I have a nice free four wheeler. As a result I am very new to these things, but have plenty of wrenching experience as a result of an often broke old Bimmer. Thanks for any help or explanations on this spraying gear oil situation!