Tractor Repair: 2590 case hyd problems, suction tubes, torque tube

Question
I am working on a 2590 case. all the hydrolics quit working and sure enough the pto was shot and plugged the suction screen and i cleaned that and rebuilt the pto.  the problem im having after i got done with that is i still have no hyd pressure and the charge pump under has a vacum instead of having pressure.  when i let the tractor sit with both suction tubes off the piston and gear pump oil runs out but when i start the tractor it sucks the oil back and it will suck ur finger right to the tubes.  have you ever ran in to this problem or heard of it??  it seems like the charge pump is pumping backwards.  thanks for your help

Answer
 The suction screeen is between the transmission housing and torque tube, so I assume you tried to clean it the best you could from the back with the pto housing removed.  Otherwise you have to split the tractor to get at the screen.  If the screen is fairly clean and the filters have been replaced ( I assume you changed the filters ), the charge pump could be worn out.  It's not possible for it to pump backwards, but if it can't get any oil or there's something wrong with it there could be some suction on the discharge side.