Hydro 84 weak forward

[Lamcmillen]

Hello, 

I’m wondering if anyone could give me pointers on my Hydro 84s lack of forward power. I’ve worked through the repair manual’s diagnostic steps. The charge pressure is correct. The drive pressure in capsule A is correct, but the psi in capsule B stays at around 500psi. I’ve swapped the forward and backward check valves. The next step in the manual would be to isolate the drive control valve but I’m not sure how I would rig something up for that. 
 

I also changed the filter and put new fluid in. The old fluid was dark.