TG1860G - Rebuilt HST, now no forward/reverse

[orangekuby]

I rebuilt my HST, a lot of new internals and took pretty good care to get everything back together the way it came apart (mostly only one way it can go together). I put new o-rings on, which was only a hand full. The pedal rod is connected to the HST and I can see it actuate the arm on the HST back and forth for both directions. The belts are connected from the engine back to the HST, I can watch the fan spin which should be turning the internal fluid sump pump.

I can turn the wheels by hand and watch the drive/brake shaft turn, and also pull the neutral switch blade on the top (to move with engine off) and hear it relieve pressure from the larger internal pump, but there is absolutely nothing when pushing on the pedals. Does not even try to move in any direction, even if you give it a slight push. It acts as if it's in neutral the entire time.

Any thoughts? I don't have any parts left over, and checked everything off the diagrams as I went to make sure I didn't miss anything. I'm kind of at a loss on what to check now.

Is there an air bleeding procedure I'm not aware of? Do I just keep holding the pedal in one direction to bleed the air? I filled it with 3 quarts as the manual says, which is essentially full to the top near the breather.

 

[orangekuby]

I tried doing the air purge method husqvarna and JD use for their HST's (couldn't find one for kubota), and I can get some of the air worked through. Hold the neutral switch, push pedal forward, reverse, repeat X times. Then release neutral switch and try moving. There is some tire movement, but the pressure quickly bleeds off and the tires stop. If I wait a minute between purging and trying to move the tires will not move.

Again, I'm stumped on where it'd bleed pressure off to/from. The HST had plenty of pressure and moved as it should (kind of, gears broke) before the rebuild. The pump mating surfaces to the pump housing were perfectly smooth still and slid easily with no burrs.

 

[North Idaho Wolfman]

If it acts like it's in neutral, something is wrong with the setup, there should be resistance on the unit, Only lift one rear tire to test, if you lift both the differential will just spin the other tire in reverse, so you won't feel any resistance.

Does it have a spin on filter? Sorry on a dumb (backup) computer so no WSM's or blueprints on this one to look at).
If it does try loosening the filter and see if it will purge fluid.

 

[orangekuby]

There is definitely resistance in the wheels. I can't push it forward without pulling the neutral or free wheel lever. There's also no external filter on this hydro, only an internal that's not serviceable without removing the bottom cover.

When trying to purge the air, while the free wheel lever is pulled, and the forward pedal is down, I can hear the typical wine. When the free wheel lever is not pulled, forward pedal down and I get the slight wheel rotation before it stops, it makes a loud wine and acts like it's sticking, then quickly stops.

The free wheel lever on this transmission is basically a little internal tab that separates the drive pump from the pump housing, allowing fluid to flow past the pump without issue, it's a very simple disengage method.

There is a small check valve/ball on the bottom on the transmission cover, I believe it's a sump pump or charge pump relief valve. I'm thinking this spring could have been knocked over when I put the cover on. Would this check ball not working cause what I'm experiencing?

 

[lugbolt]

There is a check ball & spring that likes to fall out. If not reinstalled in the correct place, it won't move.

Been there done that about a half dozen times, and Hydrogear (maker of the transmission) won't/can't tell you where it goes because they no longer have a good diagram for them.

 

[orangekuby]

Thank you for the pointers guys. It helped me get thinking about where I could have gone wrong, and was just about to take the pan cover off when I noticed the charge pump cover on the bottom has a dot on one side. I went back and looked at some pictures I took from the tear down, and sure enough I reinstalled it 180 degrees from original. Basically, the charge pump was pulling fluid away from the primary pump instead of supplying it.

Anyway, I flipped the charge pump cover around (it is elongated to one side), and now it is working 100%. Full power, chirps the tires from a stand still, and skids them coming to a stop (I know, that's not good for it). No air purge necessary.

 

[SidecarFlip]

Sounds like you have the same Hydro Gear units I have on my Cub 60" tank and I did the same thing, put the charge pump cover on backwards. Mine wouldn't do squat either and I didn't take pictures. Just on a lark I rotated the cover 180 degrees and all was well again.

Interesting that HG recommends regular multi grade motor oil for the fluid. I use Rotella T6 in mine.

 

[orangekuby]

I'm not sure if it's a hydro gear transmission, but maybe? It also calls for hydraulic UDT/UDT2 fluid instead of motor oil. I believe it's similar to the diesel models that were shaft driven instead of belt driven, but could be mistaken.

 

[lugbolt]

? It also calls for hydraulic UDT/UDT2 fluid instead of motor oil. I believe .

wrong.
20w50.

 

[bwritt2]

There is definitely resistance in the wheels. I can't push it forward without pulling the neutral or free wheel lever. There's also no external filter on this hydro, only an internal that's not serviceable without removing the bottom cover.

When trying to purge the air, while the free wheel lever is pulled, and the forward pedal is down, I can hear the typical wine. When the free wheel lever is not pulled, forward pedal down and I get the slight wheel rotation before it stops, it makes a loud wine and acts like it's sticking, then quickly stops.

The free wheel lever on this transmission is basically a little internal tab that separates the drive pump from the pump housing, allowing fluid to flow past the pump without issue, it's a very simple disengage method.

There is a small check valve/ball on the bottom on the transmission cover, I believe it's a sump pump or charge pump relief valve. I'm thinking this spring could have been knocked over when I put the cover on. Would this check ball not working cause what I'm experiencing?

Did you have any power to the wheels what so ever? Im having an issue where from low to mid throttle I have great throttle but at full throttle...nothing. I put the recommended fluid in the transmission by the manufacturer and tried to purge as much air out of the system as possible. I looked at the charge pump and it seems to be in the right orientation. Im not sure If the transmission is shot or what is happening at higher rotational speeds. Could it be to thin of a fluid for the pump? My kubota tg1860 has 830 hours and this is the first time Ive changed the hydro fluid. Anything helps

 

[D2Cat]

i think the Kubota techs suggest not changing the hyd fluid on those machines because they are a sealed unit. Maybe I'm thinking of something else !

 

[lugbolt]

i think the Kubota techs suggest not changing the hyd fluid on those machines because they are a sealed unit. Maybe I'm thinking of something else !

you are correct

if it's leaking fix it. If not, leave it alone. Changing the filter and fluid can sometimes cause more problem than leaving it alone.

 

[bwritt2]

you are correct

if it's leaking fix it. If not, leave it alone. Changing the filter and fluid can sometimes cause more problem than leaving it alone.

Its interesting because the manual has a change interval for the fluid but no public process to go about changing it. They do include instructions on how to service the gear fluid. I don't think its a lifetime fluid because 20w-50 hydrostatic fluid will break down over time decreasing its lubricity. I'm just assuming they wanted certified Kubota technicians to do it instead of the owner of the mower.

 

[D2Cat]

See post #12. He's been a certified Kubota tech for like 30 years.

 

[lugbolt]

Its interesting because the manual has a change interval for the fluid but no public process to go about changing it. They do include instructions on how to service the gear fluid. I don't think its a lifetime fluid because 20w-50 hydrostatic fluid will break down over time decreasing its lubricity. I'm just assuming they wanted certified Kubota technicians to do it instead of the owner of the mower.

the books are written by japanese and translated to engrish.

They are notoriously incorrect in certain areas and that's one of them.

but whatever. Go ahead and pull it apart to replace the filter and see how it goes. At least one pan bolt will break during removal so you'll have to drill that out. And there's other issues too of which there is zero information for (if/when it happens) in the kubota manual as well as the hydrogear manual.

I am (or was) a kubota certified elite tech and I advised folks not to mess with it unless there was a problem. Every so often someone would show up and demand an oil/filter change on the hst. Ok sure. 3 hours labor, so $300 in labor. What? For an oil change? Yep. There is no drain bolt so you have to remove the hst assembly and flip it over and let it drain. OR try to extract it but the tube won't go far enough in to get all of it out. If they wanted a filter change, same deal...add more labor, and expect additional labor for extracting broken pan bolts. I had one that was about $800 to do an oil and filter change on the HST. Broken bolts times # of hours to get them out. Then once the filter was out, sometimes a check ball would fall out and there is zero information as to where it goes. Sure, just figure it out. There are about 3 or 4 places that it can go and the transmission won't work if it's not in the ONE place it's supposed to be (and that information as to where it's supposed to go is not available from kubota nor at that time hydrogear. Eenie meanie minee mo figure out where it go if it's wrong take it apart and try a different hole.