yes kyle,
that sounds more like where the problem may have been.
something in the cylinders, maybe the safety valve might of been damaged or a cylinder problem would explain that symptom better :o)

I did also swap the mast when I swaped the pump, mabey the cylinders could have had an internal problem? or mabey it was the check valves and the ones I swapped were bad, they were used check valves I found in some of our old parts. then the other trucks mast I swapped as a whole piece hoses and all and checkvalves

odd that this fixed it, good that it did

i can understand a pump causing poor lifting performance if worn out or defective but i don't see what it has to do with the lowering. The pump is not even in the equation when the lowering circuit is activated, well, unless this unit has regenerative hydraulics.
I've noticed some newer models what have this operation now like the regenerative braking etc in the drive systems.

yet another strange thing

we have a spare parts truck, so I swapped the check valves on the cylinders, that wasn't it, then swapped the manifolds, that was not it, then decided to try the pump even though I thought it tested fine.. that fixed it.

Since lift and lower are both slow, that would indicate a possible problem with the proportional valve, or a really bad check valve in one of the cylinders. Something is restricting in both directions.

Sorry for all those typos..I'm posting from a phone that has some backspace issues