You are using a puller I assume, or are you using the Hammer and pry bar method. My Grandpa used to heat the V/D up with a torch to get them off when they were stuck. Have to be carful not to catch anything on fire though. He caught an old Chevy truck on fire once when I was about 5. I was "helping" him and the engine caught on fire. Of course he couldn't move out from under the truck very fast so I ran out side, grabbed some snow and started throwing snow on the fire. Needless to say Grandpa got hit by more snow than the engine did, but he was OK. He said it was better to be cold than burnt (RIP 1923-2003).