allis chalmers 7g series b

I just aquired a Allis Chalmers 7g b. It worked good and I loaded two trucks with it, the next day I went to use it and it will not move. I suspected low fluid but there is fluid on the stick and no evidence of a leak. I changed the paper filter and cked the sump screen for clog. The pump is turning but I still have no pressure. The book shows the pump as a two stage with the outer gears scavenging and the inner gears suppling psi to the trans, but I only see two lines. I now believe the inner pump gets its oil through ports in the torque converter housing , and there is another screen that is clogged on the supply side. If anyone has any info to let me know if I am one the wright track I would realy apreachate it. Thank you, Aric