We did a lot of rework on our 88 diesel. The original hydraulics were the electric controled switches and the pump centerplate was cracked. So we had the pump rebuilt with new bearings, seals and centerplate. Then we bought a newer reservoir with levers off of Ebay. We put everything together and checked pressure. We have over 1800 psi.But when we connected to an implement, we can only raise or extend the cylinder. We cannot retract or lower. We noticed that when working the levers, we have a lot of travel upwards and the relief valve will squeal at the end of the lever stroke. When operating the levers down, there is very little travel and no noise from the relief valve. We are puzzled as to why this is and what to do next. We use the tractor to ted hay with a four basket tedder with hydraulic fold and we need the hydraulics to work properly.