Fuel leak.

I have a 97 chevy pickup 4x4 diesel truck. It has a fuel leak but heres the catch. The fuel is leaking from the drainhole in the dustcover of the transmission.I cant remove the dust cover because of the oilpan and the exhaust pipes. Now, there are no traces of fuel on the outside of transmission or coming from any fuel lines around the area. I need to know what could cause a fuel leak inbetween the tranny and engine. There is nothin leaking from fuel pump or filter.I need help.