Clutch air leak, 1999 ranger 3.0

[sahmadi]

My clutch goes flat after a couple of days in my 1999 ranger 3.0 2WD. I have done the bench bleeding of the master cylinder as well as bleeding the slave cylinder. After the bleeding, pedal gets hard and everything is fine but pedal goes soft in few days and I can't shift gears. I think I have some air leak in some line inside the trans. I am getting ready to take down the transmission but don't realy know what to look for to fiind the leak. I appreciate any advise and ideas to solve this problem. Thank you