I just acquired an older DH4B, Mitsubishi diesel, runs fantastic, backhoe works, but the trenching chain does not. If I pull the lever to move the chain forward or backwards, it will move JUST SLIGHTLY. Maybe one tooth, then stop. You can hear the hydraulic pump working, but nothing is happening. The linkage on the pump is free and you can see it move no problem. On top and on bottom of the pump looks to be two compression style clamps that turn a rod that passes all the way through the pump. They look like they can be adjusted, but I am afraid there is something more going on here. I have plenty of hydraulic fluid and the engine revs up just fine when more RPMs are needed. I should also note that the push blade in the front does not move at all. It is almost like there is no hydraulic pressure going to the valve body. I am wondering if I am missing a hydraulic line altogether. Any ideas would be great.