hydraulic pump (again)

[washita]

on my 2007 model 425 the pistons in the fwd/rev. control would not fully seat and produce a whining sound (cavitation?) this started at roughly 300 hours, until it stuck in fwd (up a tree with the pt thread) until this happened I was unable to pinpoint the problem, repaired once, problem starting to resurface again after ten hours, personally I feel the pistons in the pedal control should have spring-loaded resistance or mechanical linkage of some type or form to prevent this problem, I would speculate if the seals are compatible with the oil in the system, our shop built 200 valve bodies with incorrect type of seals once

 

[3238dpw]

I know I don't know as much as much as many on here, but one question that struck me was, are you bleeding the system after changing the filter? I wasn't sure if you bought it used or not, but if you did you may not have gotten the manual and might not be aware. Just want to eliminate all the simple things