from my past experience ....you may need to "tap " (lol !) the cover to loosen it some before it will move.....it's amazing how something that's bathed in oil can be corroded around the sealing ring....

 

Thanks for the advice everyone. I was prepping to take the whole box out. While doing that I was straightening a bent washer on the bottom of the drop arm. I was shocked to see it pushed up the top plate. I was then able to loses the set screw with an allen wrench and unscrew the top plate. I replaced the o ring on the top plate and put it all back together and filled with fluid. As of this morning not a drop of fluid in the drip pan.

Looks like I got it. Knock on wood. I'm guessing it saved me around $500