Does the bpl 500 have a accumulator ? If so charge or replace .

Where did you buy your wear parts from? Did you have this problem before you changed your parts out?

It does not have an accumulator. To eliminate anything to do with the parts i have loosened the cover plate and valve slides over niely with a 24in wrench. Also today after cleaning out dampner and stroke limiter i now have those back. Also now today i have a new scenario. In pump forward still doesnt center over pass valve but does driver fine. but now in reverse it does go over passenger side but doesnt go over drivers...as in problem is reversed. But in reverse it tends to kinda just do whatever it wants but does often for 3-4 cycles relpicate the initial forward problem but in reverse. Seems like a one way or something...

My guess would be a shift cylinder that has bad piston seals . Better yet call schwing service .

well turns out was multiple one ways....I had a new one way that i had systematicaly exchanged with all the existing one way but guess that only works if you have one that fails.

sounds like switching valve or MPS bypass or weak signal to shift rock valve.  had a couple of 750 around that vintage that we had to put throttle valves in to delay the shift so the rock would go completly over before the diff's changed direction.

yeah actually turns outs out its not working again. worked ok for about a few yards and crapped out again. What is the MPS valve? Changed seals in spools etc of brain. Pressure tested all one ways with porta power setup and also pressure tested shuttle valves. Also took line going from shuttle on fast switch back to pump that would regulate pressure off and capped the shuttle side which should have given the dampner circuit etc full pressure with no luck. Orifices are good on shift cyl and shift cyl fully rebuilt. Im at a loss. Next im rigging up a bunch of quarter turns and gauges to see whats happening

Do you have this problem, when you run the pump with water or dry? From your description, i would guess you have internal leakage. Have you done any rebuilds to the cylinders and pumps recently? Run the pump in reverse with water, and see if there are any hoses hotter than the others, in particular the hoses from the shift cylinder

The shifting cylinders get the signal from the S-3 valve, check for overheating inside the block, leaks and the plug flow control orifices in the NG6 valve