Kubota ZD21 hydro rebuild

[fatjay]

Ordered the new plate and gasket as well as a new filter. Does anyone know if it's safe to use assembly lube in the hydro system? Also is it the same oil as my yellow buckets of hydraulic oil from tractor supply?

 

[KWentling]

What are you going to do with the face of the housing the pistons are contained in? (for the life of me I can't think what that part is called) I'm pretty sure that needs to be lapped into the face plate. My lone experience with a piston pump was about 30 something years ago. I would just use the same oil that you are going to run in it and not assembly lube. Kubota wants you to use their UDT or Super UDT. I always figured the oil was the cheap part so I get the good stuff. You probably already know this, but every thing needs to be super clean when you go back together. Dirt kills hydraulics.

 

[fatjay]

I suppose that's true. I have pails upon pails of this stuff:
Super S SuperTrac 33 Tractor Hydraulic Fluid, 5 gal. at Tractor Supply Co.

The housing the pistons are in I've been calling the barrel. It's damaged and worn, the surface isn't flat. However the previous owner included one when he last rebuilt it. I checked it over and found it to be in perfect condition compared to the good not-worn one.

Going to run it at minimum rpm when it's back together, to mate the surfaces properly. Going to completely submerge everything multiple times before re-assembly after I run it through the parts cleaner, so everything will be coated with oil before i add the oil. I have a new filter, and going to draining the entire system.

 

[David_Kb7uns]

If it was me Super UDT but Kubota will love your business on parts orders either way,

David

 

[KWentling]

If it was me Super UDT but Kubota will love your business on parts orders either way,

David

I'm with David on the this. I wouldn't use the 303 unless maybe to just flush the system with. Did the "barrel" come with the pistons that had run in it? With the tight clearances in a piston pump the pistons are matched to the bores, You should avoid swapping pistons into other bores. Maybe if there is enough wear in them this won't be an issue other than lost performance.

 

[fatjay]

I got all the parts cleaned up. The pistons/barrels had perfect clearances/tollerances. I had a few pistons from the other barrel and used them, and the other ones, and couldn't tell the difference. Put it together with a new gasket. Went together perfectly. Added hydro fluid slowly turrning the lower barrel so it wouldn't be started dry. I drained the trans and changed the filter, filled up with 303 to the top. Hooked it all up and ran it for about 5 seconds. Checked the level, it dropped but not to much. Filled to the top again. Started again, left the cover off and watched the flow. Ran for 2-3 minutes. Tested forward and reverse, fully functional. No leaks, too.

Tomorrow I'll make a brief few passes, then drain the system and flush with travelers premium. I hope everything stays working well. I cleaned it surgically and reassembled everything with great care. If it works well, I'll buy the add on expansion tank. Until then I'll monitor the fluid closely. I'll run it a bit more tomorrow at low rpm to properly mate the surfaces.

 

[KWentling]

I looked for Travelers Premium on TSC site and only saw Travelers hydraulic oil. You better read the label. If that is what you are referring to, it's not for that use.
You would be better off staying with the 303, which says something to the effect of not recommended by any OEM after 1974. I'm not saying that you have to use Kubota's oil, there are several approved substitutes, but not all hydraulic oils are created equal. I'd hate to see your hard work go to waste over trying to save a few bucks on oil. Congratulations on a successful repair!

 

[fatjay]

Traveller Premium Universal Tractor Trans/Hydraulic Fluid at Tractor Supply Co.

From the description:

Employs a common sump to lubricate hydrostatic transmissions, differentials, wet brakes, hydraulics and final drives gears

Is that not suitable? If not, what are my options, and what can I get on a Sunday?

 

[KWentling]

I couldn't find Travelers Premium, only Travelers Hydraulic. What you linked to would probably be OK going by their description. I don't see where it says that it meets anyones requirements, so your guess is as good as mine if it meets Kubota's requirements. You already know what my opinion is on oils. I would guess that is about your only option on a Sunday.

 

[fatjay]

The only source of kubota fluids is over an hour drive, or the internet. Not exactly an ideal situation. Unless planning well in advance or keep a stockpile on hand, it's difficult. Now with 2 kubota's, it'll probably be a bit more realistic to keep some fluids on hand.