I have a 640b with the scraper box on the back and it lifts real slow. No power. Everything else works good. I believe that the rear lift arm are powered by a internal pump, and I think that pump is going bad. Does anyone have experience with this models?
On this tractor, that's a totally separate system. As far as I can tell, the loader, clam, sidelinks, center links, and rippers run off a pump on the front of the crank. The power steering runs on a separate system too, that pump is on the side of the motor. It appears that the only thing the internal pump powers is the lift arms. I have checked the internal pickup screen under the tractor, and have changed the adjustment on the 3pt speed controle. Seems that mostly slows the decent. I have found a real good dealer that has actually helped me a little. Monday I will check the internal pump pressure and if it's low, I'm going to try to find the bypass valve and try to adjust it. If I can't get the pressure up, I think I will hafta dig into the tractor and try to replace the internal pump. Maybe the bypass has a bad spring? What do you think? Advise would be appreciated. Thing is I'm a pretty good mechanic, I just don't wanna hafta go through the learning curve. I'm more of a Hotrod and Harley guy.