This is one for you experts.. This is the history of what I've done and tried to do. I have a 642 that had a broken input shaft into the hydraulic pump. Everything worked fine when the shaft broke. I replaced the shaft and am fairly confident that I put it together correctly. Now the machine won't move. All other hydraulics work fine. If you stand in front of the skid loader and look at the pump, there are 3 hoses on the left (as you look toward the rear). I took the first two hoses loose and removed the micro filter and cleaned it. The left side only drive motor worked for about 5 minutes and then quit. The right side never did work. It seems that if I take the hoses loose and then put them back on the left side will work for a few minutes. Things I checked: the keyways are OK. There is plenty of hydraulic oil in the system. I believe that it's not getting enough oil pressure to the hydraulic motors. Do you think it could be the cold weather bypass valve? Or the neutral bypass valve? I'm stumped! Help!