Hitachi ex35 slow hydraulics

[MasterofDiaster221]

I got a Hitachi ex35 excavator that got real slow on all the functions hard to even tell a difference between high and slow drive speed. I changed all hydraulic filters,pulled screen out of tank and cleaned it.Went ahead and changed fluid also change the pilot control filter, tank hydraulic filter and cleaned out the strainer bit no signs of trash. Put some gauges on the machine and dead headed each functions and all functions was at the 2800-3000 psi mark and pilots pressure around 450psi. Pulled case drain lines off the machine to check drive motors and there was just a drip in high and low.also checked my pressure when in high speed and was when petal was pressed pilot pressure was put to the line so all is good just wondering if the pressure could be normal but could flow be down?? Once the pumps slowed down the pumps started to whine. Looking for possibly a service manual or info on things to test before spending more money

 

[mg2361]

If this machine is the same as a 35ZTS mentioned in your other post then the system pressure spec is 3128 ± 142 psi. The pilot pressure spec is 640 ± 70 psi (both pressures checked at fast idle with oil at 120 ± 10°F).

 

[DGODGR]

I got a Hitachi ex35 excavator that got real slow on all the functions hard to even tell a difference between high and slow drive speed. I changed all hydraulic filters,pulled screen out of tank and cleaned it.Went ahead and changed fluid also change the pilot control filter, tank hydraulic filter and cleaned out the strainer bit no signs of trash. Put some gauges on the machine and dead headed each functions and all functions was at the 2800-3000 psi mark and pilots pressure around 450psi. Pulled case drain lines off the machine to check drive motors and there was just a drip in high and low.also checked my pressure when in high speed and was when petal was pressed pilot pressure was put to the line so all is good just wondering if the pressure could be normal but could flow be down?? Once the pumps slowed down the pumps started to whine. Looking for possibly a service manual or info on things to test before spending more money

I think pump pressures could be normal with restricted flow. When checking pressures did you use a flow meter? That should have given you the opportunity to check check both pressure and flow.
I hate to offer such a simple suggestion/possible solution but I would ask if you have a pattern changer on your machine. If so, I would suggest that you check to see if the changer is in between the (2) possible pattern selections. If so this would restrict function flow but allow full pressures. I have had this happen on my Bobcat 435. The pattern selector lever was inside the cab and the operator could accidentally hit it with the right heel and it would often get bumped to the in between position. The hydraulics got pretty slow in that position. The caveat to that theory is that I'm not sure if that would have any effect to the travel motors like what you have described as one of your symptoms.