1990 520H Hydro Change Procedure

[Vixmith 25]

Wow....  A long , but interesting discussion thread.

just about whether to keep Teflon and other trash out of the Hydrostatic transmission and Hydraulic system...

Yes, Keep it out.

Most all hydraulic systems use a suction strainer - a metal screen of not-too-fine mesh.  This is to keep catastrophes out of the pump without causing cavitation by choking the pump inlet.  Cavitation rapidly accelerates pump wear.  After the pump, a very few hydraulic systems use a pressure-side filter.  Such a filter will have a cast steel housing with disposable element inside, all designed to contain the hydraulic pressure without creating high pressure drop across the filter element.

Following the control valve(s) and actuators or hydraulic motors, most hydraulic systems then have a spin-on can filter in the line where oil returns to reservoir. 
Both the high pressure filter and the return line filters will have a bypass valve method so that oil flow is not impeded by a blocked filter.  This is usually a spring holding the filter element that allows the element to be bypassed by oil flow when the pressure drop across the element exceeds design limit.

The transmission and hydraulic pump on our 520H's and other WH stalwarts will not be happy if we let any Teflon enter them.

Thanx BuKu for all the discussion on this thread.

[Phatboy 565]

2 hours ago, cleat said:

My diesel tractor has it's filter on the suction side.

 

Obviously at this position it is a fairly large micron filter.

 

As for the Wheel Horse 1100, You can follow the path from the charge pump to the control valve back to the filter and then back to the rear end housing.

This is only for the hydraulic lift, the filter does nothing at all for the motion control.

 

Well ya cant say the filter does nothing for the motion control cause the lift and the motion control share the same resovior ,, so all the oil is mixed up and filtered once it is used ,, even if it is only filtered at the lift side it still is filtered then enters back into the sump (transaxel) so all the oil eventually goes threw the filter at one time or another...

[cleat 6,344]

All sucked up fluid will eventually pass through the filter, you are correct.

 

All of the old machines I have dragged home have had clean looking fluid in them.

I do not believe that they had proper maintenance either, likely the filter old as they were, kept the fluid looking clean.

 

Of course they get new fluid and filters as soon as I get them.

 

[Ksaunders 4]

I have just bought a used toro wheel horse 520 series the dipstick under the seat is in the low range whatype of oil do i put in my tranxmission

[WVHillbilly520H 10,374]

7 hours ago, Ksaunders said:

I have just bought a used toro wheel horse 520 series the dipstick under the seat is in the low range whatype of oil do i put in my tranxmission

10w30 motor oil from the factory but who knows what the owners before you used, probably should go ahead drain and new filter and oil...also if you haven't go to the manuals section and down the appropriate onwer/operators manual for your particular 520.