do I need to move the crossmember?

[Nate003]

I serviced my transmission and put on a new tranny pan gasket right before installing the motor and tranny into my truck, I drove the truck for about 6 months. I then parked it for just over a year. It was in perfect running order, now I went to start it, and it started right up, but the transmission looks like it leaked all its fluid out. I jacked up the truck and it seems to be out of the transmission pan. The tranny pan bolts were about 1/4 turn loose, so i tighten all the one's i could get to. There are 3 that the crossmember block. after that it still leaked fluid, So i'm wondering what's the best/easiest way to change the pan gasket and is there any other area's to check for leaks after it sitting for 1 year? It leaked a huge pile under the truck. Thanks for the help.